Install ammintrin.h in the cmake build.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@157639 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Headers/CMakeLists.txt b/lib/Headers/CMakeLists.txt
index 78141a3..3c58a82 100644
--- a/lib/Headers/CMakeLists.txt
+++ b/lib/Headers/CMakeLists.txt
@@ -1,5 +1,6 @@
 set(files
   altivec.h
+  ammintrin.h
   avxintrin.h
   avx2intrin.h
   bmiintrin.h