libstdc++: Build libstdc++_libbacktrace.a as PIC [PR111936]
In order for std::stacktrace to be used in a shared library, the
libbacktrace symbols need to be built with -fPIC. Add the libtool
-prefer-pic flag to the commands in src/libbacktrace/Makefile so that
the archive contains PIC objects.
libstdc++-v3/ChangeLog:
PR libstdc++/111936
* src/libbacktrace/Makefile.am: Add -prefer-pic to libtool
compile commands.
* src/libbacktrace/Makefile.in: Regenerate.
(cherry picked from commit
f32c1e1e96ffef6512ce025942b51f3967a3e7f2)