Merge #15983: build with -fstack-reuse=none

faf38bc build with -fstack-reuse=none (MarcoFalke)

Pull request description:

  All versions of gcc that we commonly use for building are subject to bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set `-fstack-reuse=none` for all builds. See bitcoin/bitcoin#15959 (comment)

  This option does not exist for clang https://clang.llvm.org/docs/ClangCommandLineReference.html#target-independent-compilation-options, but it does for gcc https://gcc.gnu.org/onlinedocs/gcc/Code-Gen-Options.html

ACKs for commit faf38b:

Tree-SHA512: f5597583402d31ea7b89ac358a6f4a537bbb82a1dde2bd41bac65ee0fd88c7af75ee4c24c6b8eed6b139bf4dbf07ab2987f8fc30fb3eab179cd2d753a8a2a47d

Author: MarcoFalke

configure.ac

@@ -734,6 +734,10 @@ if test x$TARGET_OS != xwindows; then
   AX_CHECK_COMPILE_FLAG([-fPIC],[PIC_FLAGS="-fPIC"])
 fi
 
+# All versions of gcc that we commonly use for building are subject to bug
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set
+# -fstack-reuse=none for all gcc builds. (Only gcc understands this flag)
+AX_CHECK_COMPILE_FLAG([-fstack-reuse=none],[HARDENED_CXXFLAGS="$HARDENED_CXXFLAGS -fstack-reuse=none"])
 if test x$use_hardening != xno; then
   use_hardening=yes
   AX_CHECK_COMPILE_FLAG([-Wstack-protector],[HARDENED_CXXFLAGS="$HARDENED_CXXFLAGS -Wstack-protector"])