Fix pragma clang warning with gcc

When compiling with gcc a warning will appear for #pragma clang as
it will be ignored. Add a conditional compile so only armclang
will see the pragma clang.

Source/StatisticsFunctions/arm_mse_f64.c

@@ -111,7 +111,8 @@ void arm_mse_f64(
 #endif
 #endif
 
-#if defined(ARM_MATH_NEON) && defined(__aarch64__)
+#if defined(__ARMCC_VERSION) && (__ARMCC_VERSION >= 6010050) && \
+    defined(ARM_MATH_NEON) && defined(__aarch64__)
     #pragma clang loop vectorize(enable) unroll(disable)
 #endif
     while (blkCnt > 0U)