[RFC] libstdc++: Make --enable-libstdcxx-backtrace=auto default to yes

[Jonathan Wakely]

Any objections to this? It's a C++23 feture, so should be enabled by
default.

-- >8 --

This causes libstdc++_libbacktrace.a to be built by default. This might
fail on some targets, in which case we can make the 'auto' choice expand
to either 'yes' or 'no' depending on the target.

libstdc++-v3/ChangeLog:

	* acinclude.m4 (GLIBCXX_ENABLE_BACKTRACE): Default to yes.
	* configure: Regenerate.
---
 libstdc++-v3/acinclude.m4 | 2 +-
 libstdc++-v3/configure    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index b25378eaace..50c808c6b2d 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -5481,7 +5481,7 @@ BACKTRACE_CPPFLAGS="$BACKTRACE_CPPFLAGS -DBACKTRACE_ELF_SIZE=$elfsize"
 
   AC_MSG_CHECKING([whether to build libbacktrace support])
   if test "$enable_libstdcxx_backtrace" = "auto"; then
-    enable_libstdcxx_backtrace=no
+    enable_libstdcxx_backtrace=yes
   fi
   AC_MSG_RESULT($enable_libstdcxx_backtrace)
   if test "$enable_libstdcxx_backtrace" = "yes"; then