[docs] fix cmake code-block warning

This will unblock the llvm-sphinx-buildbot, which is currently failing due
to a warning being treated as error.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276100 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CMakePrimer.rst

@@ -246,11 +246,11 @@ In general CMake if blocks work the way you'd expect:
 .. code-block:: cmake
 
   if(<condition>)
-    .. do stuff
+    message("do stuff")
   elseif(<condition>)
-    .. do other stuff
+    message("do other stuff")
   else()
-    .. do other other stuff
+    message("do other other stuff")
   endif()
 
 The single most important thing to know about CMake's if blocks coming from a C
@@ -265,7 +265,7 @@ The most common form of the CMake ``foreach`` block is:
 .. code-block:: cmake
 
   foreach(var ...)
-    .. do stuff
+    message("do stuff")
   endforeach()
 
 The variable argument portion of the ``foreach`` block can contain dereferenced