Move MBEDTLS_COMPILER_IS_GCC & MBEDTLS_GCC_VERSION into build_info

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/include/mbedtls/build_info.h b/include/mbedtls/build_info.h
index 7a70e25..c0b724c 100644
--- a/include/mbedtls/build_info.h
+++ b/include/mbedtls/build_info.h
@@ -83,6 +83,14 @@
 #endif
 #endif
 
+#if defined(__GNUC__) && !defined(__ARMCC_VERSION) && !defined(__clang__) \
+    && !defined(__llvm__) && !defined(__INTEL_COMPILER)
+/* Defined if the compiler really is gcc and not clang, etc */
+#define MBEDTLS_COMPILER_IS_GCC
+#define MBEDTLS_GCC_VERSION \
+    (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
+#endif
+
 #if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_DEPRECATE)
 #define _CRT_SECURE_NO_DEPRECATE 1
 #endif