add min-llvm version to reduction tests

Author: gnzlbg

src/test/run-pass/simd-intrinsic-generic-reduction.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// min-llvm-version 5.0
+
 // Test that the simd_reduce_{op} intrinsics produce the correct results.
 
 #![feature(repr_simd, platform_intrinsics)]