elfdeps: Introduce --add-arch

[susematz]

this adds a facility that helps with cross compilation and automatic
ELF dependencies by extending the existing mechanism to specially mark
generated ELF deps with "(lib64)" suffixes to alternatively or
additionally include an architecture name. This is enabled with
the --add-arch option.

Additionally it's possible to disable generation of unsuffixed deps
with --no-nonarch, so that the old names can gradually be phased out
(by leaving them in the generated Provides, but remove them from
the Requires). Some examples with random libs I happen to have lying
around:

% ./elfdeps --requires --add-arch --no-nonarch /matz/debian/root.riscv64/lib/riscv64-linux-gnu/libreadline.so.7
ld-linux-riscv64-lp64d.so.1(GLIBC_2.27)(riscv64)
libtinfo.so.6(NCURSES6_TINFO_5.0.19991023)(riscv64)
libc.so.6(GLIBC_2.27)(riscv64)
libtinfo.so.6()(riscv64)
libc.so.6()(riscv64)
ld-linux-riscv64-lp64d.so.1()(riscv64)
rtld(GNU_HASH)

Note how the "(lib64)" markers are not generated here (--no-nonarch), but ...

% ./elfdeps --provides --add-arch /matz/debian/root.riscv64/lib/riscv64-linux-gnu/libreadline.so.7
libreadline.so.7()(64bit)
libreadline.so.7()(riscv64)

... are generated here. Further (mixing several arch libs):

% ./elfdeps --requires --add-arch --no-nonarch /matz/debian/root.arm64/lib/libxtables.so.10 /lib64/libutil.so.1 /lib/libreadline.so.8
ld-linux-aarch64.so.1(GLIBC_2.17)(aarch64)
libdl.so.2(GLIBC_2.17)(aarch64)
libc.so.6(GLIBC_2.17)(aarch64)
libdl.so.2()(aarch64)
libc.so.6()(aarch64)
ld-linux-aarch64.so.1()(aarch64)
rtld(GNU_HASH)
libc.so.6(GLIBC_2.4)(x86_64)
libc.so.6(GLIBC_PRIVATE)(x86_64)
libc.so.6(GLIBC_2.2.5)(x86_64)
libc.so.6()(x86_64)
libtinfo.so.6(NCURSES6_TINFO_5.0.19991023)(i386)
libc.so.6(GLIBC_2.28)(i386)
libc.so.6(GLIBC_2.11)(i386)
libc.so.6(GLIBC_2.2)(i386)
libc.so.6(GLIBC_2.1.3)(i386)
libc.so.6(GLIBC_2.2.3)(i386)
libc.so.6(GLIBC_2.15)(i386)
libc.so.6(GLIBC_2.4)(i386)
libc.so.6(GLIBC_2.1)(i386)
libc.so.6(GLIBC_2.3.4)(i386)
libc.so.6(GLIBC_2.0)(i386)
libc.so.6(GLIBC_2.3)(i386)
libtinfo.so.6()(i386)
libc.so.6()(i386)

[pmatilai]

Just noting that there's significant overlap with #1038

[susematz]

Wow, looks really similar indeed. It was a result of a specific local project and I didn't know about #1038, so let that be an indication that something like this would be really welcome.

[Conan-Kudo]

Yep, I worked on #1038 to solve this and several other problems I was having in OpenMandriva. Alas, it's stuck for now. 😭

[susematz]

So, how to move forward? I'd like to at least have the possibility to enable such dependencies, with default behaviour as traditional (i.e. "(64bit)" markers), but for that at least the changes to elfdeps.c need to be done. I've consciously left out changes for elf.attr and elflib.attr .

[pmatilai]

Lets continue in #1038 as there's more background and context there.