configure: add -Wformat to CFLAGS

Without -Wformat for -Wformat-security, gcc will complain:

checking whether the C compiler accepts -Wformat-security... no
configure: error: Cannot enable -Wformat-security, consider configuring with --disable-hardening

Related to: tpm2-software#899

Signed-off-by: Bill Roberts <bill.c.roberts@gmail.com>

Author: williamcroberts

configure.ac

@@ -520,7 +520,7 @@ AS_IF([test x"$enable_hardening" != xno], [
   AS_IF([test "x$ax_is_release" = "xno"], [add_hardened_c_flag([-Werror])])
 
   add_hardened_c_flag([-Wformat])
-  add_hardened_c_flag([-Wformat-security])
+  add_hardened_c_flag([-Wformat -Wformat-security])
   add_hardened_c_flag([-Wstack-protector])
   add_hardened_c_flag([-fstack-protector-all])
   add_hardened_c_flag([-Wstrict-overflow=5])