Merge bitcoin/bitcoin#28672: build: move -fstack-reuse=none to CORE_CXXFLAGS

8cfa22a build: move -fstack-reuse=none to CORE_CXXFLAGS (fanquake)

Pull request description:

  This is not a hardening specific flag, it should be used at all times, regardless of if hardening is enabled or not. Note that this was still the case here, but having this exist in the hardening flags is confusing, and may lead someone to move it inside one of the `use_hardening` blocks, where it would become unused, with `--disable-hardening`.

  Noticed while reviewing hebasto/bitcoin#32 (comment).

ACKs for top commit:
  theuni:
    ACK 8cfa22a. Agree it's confusing as-is and this better matches the intent.
  hebasto:
    ACK 8cfa22a
  luke-jr:
    utACK 8cfa22a
  TheCharlatan:
    ACK 8cfa22a

Tree-SHA512: 74c3219301398361d06b1ef2257fc9ec18055b1661f8733ee909adefee61e458d70991c32adf0e0450905a7ffbddc99799f5fdac894f4896cfade19f961818df

Author: fanquake

configure.ac

@@ -471,6 +471,12 @@ fi
 dnl Don't allow extended (non-ASCII) symbols in identifiers. This is easier for code review.
 AX_CHECK_COMPILE_FLAG([-fno-extended-identifiers], [CORE_CXXFLAGS="$CORE_CXXFLAGS -fno-extended-identifiers"], [], [$CXXFLAG_WERROR])
 
+dnl Currently all versions of gcc are subject to a class of bugs, see the
+dnl gccbug_90348 test case (only reproduces on GCC 11 and earlier) and
+dnl https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111843. To work around that, set
+dnl -fstack-reuse=none for all gcc builds. (Only gcc understands this flag)
+AX_CHECK_COMPILE_FLAG([-fstack-reuse=none], [CORE_CXXFLAGS="$CORE_CXXFLAGS -fstack-reuse=none"])
+
 enable_arm_crc=no
 enable_arm_shani=no
 enable_sse42=no
@@ -941,11 +947,6 @@ if test "$TARGET_OS" != "windows"; then
   AX_CHECK_COMPILE_FLAG([-fPIC], [PIC_FLAGS="-fPIC"])
 fi
 
-dnl Currently all versions of gcc are subject to a class of bugs, see the
-dnl gccbug_90348 test case (only reproduces on GCC 11 and earlier) and the related bugs of
-dnl https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set
-dnl -fstack-reuse=none for all gcc builds. (Only gcc understands this flag)
-AX_CHECK_COMPILE_FLAG([-fstack-reuse=none], [HARDENED_CXXFLAGS="$HARDENED_CXXFLAGS -fstack-reuse=none"])
 if test "$use_hardening" != "no"; then
   use_hardening=yes
   AX_CHECK_COMPILE_FLAG([-Wstack-protector], [HARDENED_CXXFLAGS="$HARDENED_CXXFLAGS -Wstack-protector"])