GCC added -gz=zlib-gnu in 2014 for -gz meaning change (.zdebug =>
SHF_COMPRESSED) and the legacy zlib-gnu hasn't gain adoption.
According to Debian Code Search (`gz=zlib-gnu`), no project uses -gz=zlib-gnu
(valgrind has a configure to use -gz=zlib). Any possible -gz=zlib-gnu user can
switch to -gz smoothly (supported by integrated assemblers for many years;
binutils 2.26).
Reviewed By: dblaikie
Differential Revision: https://reviews.llvm.org/D117744
Because why would that be necessary? (I joke - I hadn't actually
expected this to be an issue but a content-hash-named filesystem means
the clang binary's just a bunch of numbers, and doesn't have 'clang'
anywhere in the name)
gcc translates -gz=zlib to --compress-debug-options=zlib for both assembler and linker
but clang only does this for assembler.
The linker needs --compress-debug-options=zlib option to compress the debug sections
in the generated executable or shared library.
Due to this bug, -gz=zlib has no effect on the generated executable or shared library.
This patch fixes that.
Differential Revision: https://reviews.llvm.org/D87321
Fangrui Song