cmake: Install CheckAtomic.cmake (needed by lldb)

[mgorny]

Summary

Install CheckAtomic.cmake along with other LLVM modules, therefore making it possible for other projects to use it. This file is needed for LLDB to be built standalone, and installing it was suggested in https://reviews.llvm.org/D23881.

[beanz]

LGTM.

[mgorny]

Thanks for the review. As usual, I forgot to mention I don't have commit access ;-).

llvm/trunk/cmake/modules/CMakeLists.txt

if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
 
   install(DIRECTORY .
     DESTINATION ${LLVM_INSTALL_PACKAGE_DIR}
     FILES_MATCHING PATTERN *.cmake
     PATTERN .svn EXCLUDE
     PATTERN LLVMConfig.cmake EXCLUDE
     PATTERN LLVMConfigVersion.cmake EXCLUDE
     PATTERN LLVM-Config.cmake EXCLUDE
-    PATTERN GetHostTriple.cmake EXCLUDE
-    PATTERN CheckAtomic.cmake EXCLUDE)
+    PATTERN GetHostTriple.cmake EXCLUDE)
 endif()