Makefile.debug: support for -gz=zstd

Make DEBUG_INFO_COMPRESSED a choice; DEBUG_INFO_COMPRESSED_NONE is the
default, DEBUG_INFO_COMPRESSED_ZLIB uses zlib,
DEBUG_INFO_COMPRESSED_ZSTD uses zstd.

This renames the existing KConfig option DEBUG_INFO_COMPRESSED to
DEBUG_INFO_COMPRESSED_ZLIB so users upgrading may need to reset the new
Kconfigs.

Some quick N=1 measurements with du, /usr/bin/time -v, and bloaty:

clang-16, x86_64 defconfig plus
CONFIG_DEBUG_INFO=y CONFIG_DEBUG_INFO_COMPRESSED_NONE=y:
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:55.43
488M vmlinux
27.6%   136Mi   0.0%       0    .debug_info
 6.1%  30.2Mi   0.0%       0    .debug_str_offsets
 3.5%  17.2Mi   0.0%       0    .debug_line
 3.3%  16.3Mi   0.0%       0    .debug_loclists
 0.9%  4.62Mi   0.0%       0    .debug_str

clang-16, x86_64 defconfig plus
CONFIG_DEBUG_INFO=y CONFIG_DEBUG_INFO_COMPRESSED_ZLIB=y:
Elapsed (wall clock) time (h:mm:ss or m:ss): 1:00.35
385M vmlinux
21.8%  85.4Mi   0.0%       0    .debug_info
 2.1%  8.26Mi   0.0%       0    .debug_str_offsets
 2.1%  8.24Mi   0.0%       0    .debug_loclists
 1.9%  7.48Mi   0.0%       0    .debug_line
 0.5%  1.94Mi   0.0%       0    .debug_str

clang-16, x86_64 defconfig plus
CONFIG_DEBUG_INFO=y CONFIG_DEBUG_INFO_COMPRESSED_ZSTD=y:
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:59.69
373M vmlinux
21.4%  81.4Mi   0.0%       0    .debug_info
 2.3%  8.85Mi   0.0%       0    .debug_loclists
 1.5%  5.71Mi   0.0%       0    .debug_line
 0.5%  1.95Mi   0.0%       0    .debug_str_offsets
 0.4%  1.62Mi   0.0%       0    .debug_str

That's only a 3.11% overall binary size savings over zlib, but at no
performance regression.

Link: https://maskray.me/blog/2022-09-09-zstd-compressed-debug-sections
Link: https://maskray.me/blog/2022-01-23-compressed-debug-sections


Suggested-by: Sedat Dilek (DHL Supply Chain) <sedat.dilek@dhl.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>