[Bug sanitizer/101111] xgcc cross-compiler for x86_64-apple-darwin in GCC 11.1 doesn't generate weak symbols, resulting in undefined reference to ___lsan_default_suppressions

[mose at gnu dot org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101111

--- Comment #5 from Mosè Giordano <mose at gnu dot org> ---
Ok, I finally found the culprit: `libsanitizer` does already have a way to add
`-Wl,-undefined,dynamic_lookup` to CXXFLAGS, but it uses a bashism:
<https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libsanitizer/configure.tgt;h=0ca5d9fd92464110d99a5da86b8de4378384e944;hb=HEAD#l68>.
 On Alpine Linux, the system where I'm doing the compilation, sh isn't bash and
appending to a string variable with += isn't valid.  Scavenging the compilation
log I found

/workspace/srcdir/gcc-11.1.0/libsanitizer/configure:
/workspace/srcdir/gcc-11.1.0/libsanitizer/configure.tgt: line 68:
EXTRA_CXXFLAGS+=-Wl,-undefined,dynamic_lookup: not found

If I replace

EXTRA_CXXFLAGS+="-Wl,-undefined,dynamic_lookup"

with

EXTRA_CXXFLAGS="${EXTRA_CXXFLAGS} -Wl,-undefined,dynamic_lookup"

compilation of GCC is finally successful.