tools/elftoolchain: Handle dependencies properly.

This should properly resolve the problem christos was trying to
address by a bogus make includes hack and #ifdefs in elftoolchain.

Build 'libelf' and 'libdwarf' under 'tools/elftoolchain', after
'tools/elftoolchain/common' has been built.

This change aligns the 'tools' build with the regular build.

Subsequent commits will change 'tools/libctf' and
'tools/cft{merge,convert}' to use the new build paths.

When building tools use a dedicated subdirectory for compiling
Elftoolchain code.

Build and install <sys/elfdefinitions.h> in ${TOOLDIR}/include.

This change prepares the ground for upgrading libelf and libdwarf to
their current Elftoolchain versions.

don't install headers as executable.

Bug fix: use the correct target path in a dependency.

Add a Makefile missed out in a previous commit.

revert previous, riastradh fixed it correctly and this is not needed.

Restore the minimum build to install elfdefinitions.h. Provide a pre-built
copy, since we don't have m4 available. Use pax to install it because
using the Makefile needs more stuff available (nbsed) which we have not
built yet.

Add ${_MKTARGET_CREATE}

don't install headers as executable.

When building tools use a dedicated subdirectory for compiling
Elftoolchain code.

Build and install <sys/elfdefinitions.h> in ${TOOLDIR}/include.

This change prepares the ground for upgrading libelf and libdwarf to
their current Elftoolchain versions.

revert previous, riastradh fixed it correctly and this is not needed.

Restore the minimum build to install elfdefinitions.h. Provide a pre-built
copy, since we don't have m4 available. Use pax to install it because
using the Makefile needs more stuff available (nbsed) which we have not
built yet.

elftoolchain: Be consistent about which ELF header files we use.

1. For tools that use elftoolchain: always use elftoolchain's
elfdefinitions.h. Don't even think about looking at the host's
sys/exec_elf.h, which makes no sense and should never happen.

(ELF tools that don't use elftoolchain, like m68k-elf2coff,
continue to use nbincludes/sys/exec_elf.h. But no more nbincludes
hacks in elftoolchain.)

2. For kernel components (solaris, zfs, dtrace): always use
sys/exec_elf.h, even in Solaris components via sys/elf.h.
elfdefinitions.h is not wired up in the kernel build at all.

3. For most userland components that involve libelf: use
elfdefinitions.h via libelf header files (libelf.h, gelf.h).

libdtrace in particular requires _all_ R_* reloc type definitions,
but sys/exec_elf.h brings in only the _current machine's_ R_*
reloc type definitions. (While here: Use uintptr_t instead of
Elf_Addr for pointer-to-integer cast, since Elf_Addr is MD and
provided only by sys/exec_elf.h, not by elfdefinitions.h.)

And most userland components using libelf don't rely on any
properties of the current machine from sys/exec_elf.h, so they can
use libelf's elfdefinition.h.

Exceptions:

- dtrace drti.c relies on link.h -> link_elf.h -> sys/exec_elf.h,
but it also relies on sys/dtrace.h -> sys/elf.h ->
elfdefinitions.h like other userland components using sys/elf.h.

- kdump-ioctl.c uses sys/exec_elf.h directly and sys/dtrace.h ->
sys/elf.h -> elfdefinitions like other userland components using
sys/elf.h.

- t_ptrace_wait.c (via t_ptrace_core_wait.h) uses libelf to parse
core files, but relies on sys/exec_elf.h for struct
netbsd_elfcore_procinfo.

None of these exceptions needs all R_* reloc type definitions, so
as a workaround, we can just suppress libelf's elfdefinitions.h by
defining _SYS_ELFDEFINITIONS_H_ and use sys/exec_elf.h in these
exceptions.

And undo the whole BUILTIN_ELF_HEADERS mistake. This was:

- half bogus workarounds for missing build_install dependencies in
tools/Makefile, which are no longer missing now, and
- half futile attempt to use src/sys/sys/exec_elf.h via nbincludes in
tools involving libelf instead of libelf's elfdefinitions.h, which
collides.

Longer-term, we may wish to unify sys/exec_elf.h and libelf's
elfdefinitions.h, so we don't have to play these games.

But at least now the games are limited to three .c files (one of
which is generated by Makefile.ioctl-c), rather than haphazardly
applied tree-wide by monstrous kludges in widely used .h files with
broken hackarounds to get the tools build lurching to completion.

tools/elftoolchain: Build with BUILTIN_ELF_HEADERS again.

The header file dependency that motivated disabling this should be
resolved now.

Remove dependency to elfdefinitions.h, this is a mess, since it needs
${TOOL_M4} which might not be available yet.

- fix nbincludes so that it can be included from any level
- add elftoolchain/common to the list of headers to be build before depend
- make libdwarf build the includes since it needs <sys/elfdefinitions.h>
which does not exist on non-netbsd systems.

changes for r4037

Make the generated <sys/elfdefinitions.h> file visible when compiling
libdwarf.

Build 'libelf' and 'libdwarf' under 'tools/elftoolchain', after
'tools/elftoolchain/common' has been built.

This change aligns the 'tools' build with the regular build.

Subsequent commits will change 'tools/libctf' and
'tools/cft{merge,convert}' to use the new build paths.

elftoolchain: Be consistent about which ELF header files we use.

1. For tools that use elftoolchain: always use elftoolchain's
elfdefinitions.h. Don't even think about looking at the host's
sys/exec_elf.h, which makes no sense and should never happen.

(ELF tools that don't use elftoolchain, like m68k-elf2coff,
continue to use nbincludes/sys/exec_elf.h. But no more nbincludes
hacks in elftoolchain.)

2. For kernel components (solaris, zfs, dtrace): always use
sys/exec_elf.h, even in Solaris components via sys/elf.h.
elfdefinitions.h is not wired up in the kernel build at all.

3. For most userland components that involve libelf: use
elfdefinitions.h via libelf header files (libelf.h, gelf.h).

libdtrace in particular requires _all_ R_* reloc type definitions,
but sys/exec_elf.h brings in only the _current machine's_ R_*
reloc type definitions. (While here: Use uintptr_t instead of
Elf_Addr for pointer-to-integer cast, since Elf_Addr is MD and
provided only by sys/exec_elf.h, not by elfdefinitions.h.)

And most userland components using libelf don't rely on any
properties of the current machine from sys/exec_elf.h, so they can
use libelf's elfdefinition.h.

Exceptions:

- dtrace drti.c relies on link.h -> link_elf.h -> sys/exec_elf.h,
but it also relies on sys/dtrace.h -> sys/elf.h ->
elfdefinitions.h like other userland components using sys/elf.h.

- kdump-ioctl.c uses sys/exec_elf.h directly and sys/dtrace.h ->
sys/elf.h -> elfdefinitions like other userland components using
sys/elf.h.

- t_ptrace_wait.c (via t_ptrace_core_wait.h) uses libelf to parse
core files, but relies on sys/exec_elf.h for struct
netbsd_elfcore_procinfo.

None of these exceptions needs all R_* reloc type definitions, so
as a workaround, we can just suppress libelf's elfdefinitions.h by
defining _SYS_ELFDEFINITIONS_H_ and use sys/exec_elf.h in these
exceptions.

And undo the whole BUILTIN_ELF_HEADERS mistake. This was:

- half bogus workarounds for missing build_install dependencies in
tools/Makefile, which are no longer missing now, and
- half futile attempt to use src/sys/sys/exec_elf.h via nbincludes in
tools involving libelf instead of libelf's elfdefinitions.h, which
collides.

Longer-term, we may wish to unify sys/exec_elf.h and libelf's
elfdefinitions.h, so we don't have to play these games.

But at least now the games are limited to three .c files (one of
which is generated by Makefile.ioctl-c), rather than haphazardly
applied tree-wide by monstrous kludges in widely used .h files with
broken hackarounds to get the tools build lurching to completion.

changes for r4037

Build 'libelf' and 'libdwarf' under 'tools/elftoolchain', after
'tools/elftoolchain/common' has been built.

This change aligns the 'tools' build with the regular build.

Subsequent commits will change 'tools/libctf' and
'tools/cft{merge,convert}' to use the new build paths.