Report errors for certain unknown section types

[MaskRay]

See also llvm/llvm-project#84812

From https://maskray.me/blog/2024-03-09-a-compact-relocation-format-for-elf#linker-notes

GNU ld allows certain unknown section types:

• [SHT_LOUSER,SHT_HIUSER] and non-SHF_ALLOC
• [SHT_LOOS,SHT_HIOS] and non-SHF_OS_NONCONFORMING

but reports errors and stops linking for others (unless --no-warn-mismatch is specified).
When linking a relocatable file using SHT_RELLEB, you might encounter errors like the following:

% clang -mrelleb -fuse-ld=bfd a.c b.c
/usr/bin/ld.bfd: unknown architecture of input file `/tmp/a-1e0778.o' is incompatible with i386:x86-64 output
/usr/bin/ld.bfd: unknown architecture of input file `/tmp/b-9963f0.o' is incompatible with i386:x86-64 output
/usr/bin/ld.bfd: error in /tmp/a-1e0778.o(.eh_frame); no .eh_frame_hdr table will be created
/usr/bin/ld.bfd: error in /tmp/b-9963f0.o(.eh_frame); no .eh_frame_hdr table will be created
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I have a prototype for a new relocation format (RELLEB). Linking a.o and b.o with unpatched gold, lld, and mold create an output file with unrelocated .text and will crash at run-time.