compiler: -fasynchronous-unwind-tables hardening

Increased reliability of backtraces.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

configure.ac

@@ -719,6 +719,7 @@ AX_CHECK_COMPILE_FLAG([-Werror=shift-count-overflow], [CFLAGS="$CFLAGS -Werror=s
 AX_CHECK_COMPILE_FLAG([-Werror=shift-overflow=2], [CFLAGS="$CFLAGS -Werror=shift-overflow=2"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wdate-time], [CFLAGS="$CFLAGS -Wdate-time"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wnested-externs], [CFLAGS="$CFLAGS -Wnested-externs"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-fasynchronous-unwind-tables], [CFLAGS="$CFLAGS -fasynchronous-unwind-tables"],,[-Werror])
 
 AX_CHECK_LINK_FLAG([-z relro], [LDLAGS="$LDLAGS -z relro"],,[])
 AX_CHECK_LINK_FLAG([-z now], [LDLAGS="$LDLAGS -z now"],,[])