CMake: Documented two cmake variables.

llvm-svn: 60008
diff --git a/llvm/docs/CMake.html b/llvm/docs/CMake.html
index f6ea666..5a088c2 100644
--- a/llvm/docs/CMake.html
+++ b/llvm/docs/CMake.html
@@ -213,6 +213,12 @@
   <dd>Path where LLVM will be installed if "make install" is invoked
     or the "INSTALL" target is built.</dd>
 
+  <dt><b>CMAKE_C_FLAGS</b>:STRING</dt>
+  <dd>Extra flags to use when compiling C source files.</dd>
+
+  <dt><b>CMAKE_CXX_FLAGS</b>:STRING</dt>
+  <dd>Extra flags to use when compiling C++ source files.</dd>
+
   <dt><b>BUILD_SHARED_LIBS</b>:BOOL</dt>
   <dd>Flag indicating is shared libraries will be built. Its default
     value is OFF. Shared libraries are not supported on Windows and