[PATCH] binutils, gdb: support zstd compressed debug sections

[Fangrui Song]

On 2022-09-19, Simon Marchi wrote:
>> I am unfamilir with autotools, but I agree that pkg-config is better.  Changed to PKG_CHECK_MODULES
>> and pushed the change to
>> https://gitlab.com/MaskRay/binutils-gdb/-/commits/zstd
>
>Thanks, I'll take a proper look when you post a v2.
>
>> However, now `make all-gdb` fails to link because gdb/Makefile does not have `ZSTD_LIBS = -lzstd` ...
>
>For GDB, you can copy what we do for debuginfod in gdb/Makefile.in,
>which would mean:
>
>ZSTD_CFLAGS = @ZSTD_CFLAGS@
>ZSTD_LIBS = @ZSTD_LIBS@
>
>And use $(ZSTD_CFLAGS) and $(ZSTD_LIBS) where appropriate.
>
>Simon

Thanks, the ZSTD_CFLAGS tip helped.  I inspected jansson and msgpack's
pkg-config check and get this v2 patch:
https://sourceware.org/pipermail/binutils/2022-September/122950.html

Note: For some reasons I have to include PKG_PROG_PKG_CONFIG in
config/zstd.m4, otherwise pkg-config does not work for some directories.

Note: PKG_CHECK_MODULES(MSGPACK in binutils/configure.ac possibly misses
AC_MSG_CHECKING/AC_MSG_RESULT, so when msgpack is missing, the log isn't
clear.