[PATCH] libstdc++: Use GLIBCXX_CHECK_LINKER_FEATURES for cross-builds (PR111238)

[Christophe Lyon]

As discussed in PR104167 (comments #8 and below), and PR111238, using
-Wl,-gc-sections in the libstdc++ testsuite for arm-eabi
(cross-toolchain) avoids link failures for a few tests:

27_io/filesystem/path/108636.cc
std/time/clock/gps/1.cc
std/time/clock/gps/io.cc
std/time/clock/tai/1.cc
std/time/clock/tai/io.cc
std/time/clock/utc/1.cc
std/time/clock/utc/io.cc
std/time/clock/utc/leap_second_info.cc
std/time/exceptions.cc
std/time/format.cc
std/time/time_zone/get_info_local.cc
std/time/time_zone/get_info_sys.cc
std/time/tzdb/1.cc
std/time/tzdb/leap_seconds.cc
std/time/tzdb_list/1.cc
std/time/zoned_time/1.cc
std/time/zoned_time/custom.cc
std/time/zoned_time/io.cc
std/time/zoned_traits.cc

This patch achieves this by calling GLIBCXX_CHECK_LINKER_FEATURES in
cross-build cases, like we already do for native builds. We keep not
doing so in Canadian-cross builds.

However, this would hide the fact that libstdc++ somehow forces the
user to use -Wl,-gc-sections to avoid undefined references to chdir,
mkdir, chmod, pathconf, ... so maybe it's better to keep the status
quo and not apply this patch?

2023-08-31  Christophe Lyon  <christophe.lyon@linaro.org>

libstdc++-v3/ChangeLog:

        PR libstdc++/111238
        * configure: Regenerate.
        * configure.ac: Call GLIBCXX_CHECK_LINKER_FEATURES in cross,
        non-Canadian builds.
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