gcc: let libstdc++ use newlib's __cxa_thread_atexit on the Vita target

libstdc++ only defers thread_local destructor registration to libc when
HAVE___CXA_THREAD_ATEXIT is defined at its configure time, and the
--with-newlib branch never checks for the symbol: it hardcodes its
feature list. Without the define, libsupc++ compiles its own fallback,
which keeps the destructor list in a pthread key, only runs it when the
prebuilt library sees gthreads as active (a weak pthread_cancel
reference, satisfied only by a whole-archive libpthread), and never on a
raw kernel thread. Newlib on Vita now provides __cxa_thread_atexit,
running the destructors from the thread-exit path on every exit path, so
define it for arm-vita-eabi in that branch. Patched in both configure.ac
and the generated configure, since the build does not regenerate it.

Assisted-by: Claude Fable 5

Author: frangarcj

cmake/recipes/GccCommonArgs.cmake

@@ -13,7 +13,8 @@ set(gcc_patch_series
     "${PROJECT_SOURCE_DIR}/patches/gcc/0001-vita-target.patch|1"
     "${PROJECT_SOURCE_DIR}/patches/gcc/0002-vita-driver.patch|1"
     "${PROJECT_SOURCE_DIR}/patches/gcc/0003-libgomp-vita.patch|1"
-    "${PROJECT_SOURCE_DIR}/patches/gcc/0004-host-compat.patch|1")
+    "${PROJECT_SOURCE_DIR}/patches/gcc/0004-host-compat.patch|1"
+    "${PROJECT_SOURCE_DIR}/patches/gcc/0005-libstdcxx-cxa-thread-atexit.patch|1")
 list(JOIN gcc_patch_series "^" gcc_patch_series_arg)
 if("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" AND ${CMAKE_SYSTEM_NAME} STREQUAL "Darwin")
     # GCC on OSX (Clang in diguise) needs more bracket nesting depth to compile gcc

patches/gcc/0005-libstdcxx-cxa-thread-atexit.patch

@@ -0,0 +1,29 @@
+--- a/libstdc++-v3/configure.ac
++++ b/libstdc++-v3/configure.ac
+@@ -339,6 +339,11 @@
+   # on a hosted environment.
+   if test "x${with_newlib}" = "xyes"; then
+     os_include_dir="os/newlib"
++    case "${host}" in
++      arm-vita-eabi*)
++        AC_DEFINE(HAVE___CXA_THREAD_ATEXIT)
++        ;;
++    esac
+     AC_DEFINE(HAVE_HYPOT)
+ 
+     # GLIBCXX_CHECK_STDLIB_SUPPORT
+--- a/libstdc++-v3/configure
++++ b/libstdc++-v3/configure
+@@ -27343,6 +27343,12 @@
+   # on a hosted environment.
+   if test "x${with_newlib}" = "xyes"; then
+     os_include_dir="os/newlib"
++    case "${host}" in
++      arm-vita-eabi*)
++        $as_echo "#define HAVE___CXA_THREAD_ATEXIT 1" >>confdefs.h
++
++        ;;
++    esac
+     $as_echo "#define HAVE_HYPOT 1" >>confdefs.h
+ 
+