libstdc++: Build libbacktrace and 19_diagnostics/stacktrace with -funwind-tables...

libstdc++: Build libbacktrace and 19_diagnostics/stacktrace with -funwind-tables [PR111641]

Several of the 19_diagnostics/stacktrace tests FAIL on Solaris/SPARC (32
and 64-bit), Solaris/x86 (32-bit only), and several other targets:

FAIL: 19_diagnostics/stacktrace/current.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/current.cc  -std=gnu++26 execution test
FAIL: 19_diagnostics/stacktrace/entry.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/entry.cc  -std=gnu++26 execution test
FAIL: 19_diagnostics/stacktrace/output.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/output.cc  -std=gnu++26 execution test
FAIL: 19_diagnostics/stacktrace/stacktrace.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/stacktrace.cc  -std=gnu++26 execution test

As it turns out, both the copy of libbacktrace in libstdc++ and the
testcases proper need to compiled with -funwind-tables, as is done for
libbacktrace itself.

This isn't an issue on Linux/x86_64 and Solaris/amd64 since 64-bit x86
always defaults to -funwind-tables.  32-bit x86 does, too, when
-fomit-frame-pointer is enabled as on Linux/i686, but unlike
Solaris/i386.

So this patch always enables the option both for the libbacktrace copy
and the testcases.

Tested on i386-pc-solaris2.11, sparc-sun-solaris2.11, and
x86_64-pc-linux-gnu.

2024-05-23  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	libstdc++-v3:
	PR libstdc++/111641
	* src/libbacktrace/Makefile.am (AM_CFLAGS): Add -funwind-tables.
	* src/libbacktrace/Makefile.in: Regenerate.

	* testsuite/19_diagnostics/stacktrace/current.cc (dg-options): Add
	-funwind-tables.
	* testsuite/19_diagnostics/stacktrace/entry.cc: Likewise.
	* testsuite/19_diagnostics/stacktrace/hash.cc: Likewise.
	* testsuite/19_diagnostics/stacktrace/output.cc: Likewise.
	* testsuite/19_diagnostics/stacktrace/stacktrace.cc: Likewise.