cleanup changes of cmake-building for Intel(R) Many Integrated Core Architecture

llvm-svn: 226272
diff --git a/openmp/runtime/cmake/BuildPLRules.cmake b/openmp/runtime/cmake/BuildPLRules.cmake
index 01af058..081c0cd 100644
--- a/openmp/runtime/cmake/BuildPLRules.cmake
+++ b/openmp/runtime/cmake/BuildPLRules.cmake
@@ -10,8 +10,9 @@
 #
 
 ###############################################################################
-# This file contains additional build rules that correspond to build.pl's rules
+# This file contains additional build rules that correspond to build.pl's rules.
 # Building libiomp5.dbg is linux only, Windows will build libiomp5md.dll.pdb
+# This file is only active if ${USE_BUILDPL_RULES} is true.
 #
 #                        ######### BUILD DEPENDENCIES ##########
 #