autotools: compiler based hardening

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

configure.ac

@@ -687,6 +687,11 @@ AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough], [CFLAGS="$CFLAGS -Wimplicit-fall
 AX_CHECK_COMPILE_FLAG([-Wcast-align], [CFLAGS="$CFLAGS -Wcast-align"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wstrict-prototypes], [CFLAGS="$CFLAGS -Wstrict-prototypes"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-fno-strict-aliasing], [CFLAGS="$CFLAGS -fno-strict-aliasing"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-fstack-clash-protection], [CFLAGS="$CFLAGS -fstack-clash-protection"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-fstack-protector-strong], [CFLAGS="$CFLAGS -fstack-protector-strong"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-g], [CFLAGS="$CFLAGS -g"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([--mcet -fcf-protection], [CFLAGS="$CFLAGS --mcet -fcf-protection"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-Werror=implicit-function-declaration], [CFLAGS="$CFLAGS -Werror=implicit-function-declaration"],,[-Werror])
 
 AX_CHECK_LINK_FLAG([-z relro], [LDLAGS="$LDLAGS -z relro"],,[])
 AX_CHECK_LINK_FLAG([-z now], [LDLAGS="$LDLAGS -z now"],,[])