[CMake] clang-*.*: Prevent versioning if the buildhost is targeting for Win32.

CMake-2.8.12 is hardcoded to create symlinked clang.exe if the target property VERSION is present and the host is not Win32.
Then clang.exe-*.* is generated and clang.exe is symlinked to it.

  lrwxrwxrwx. 1 bb bb      13 Jul  5 18:04 clang.exe -> clang.exe-3.7
  -rwxr-x---. 1 bb bb  244763 Jul  5 18:04 clang++.exe
  -rwxr-x---. 1 bb bb  244763 Jul  5 18:04 clang.exe-3.7

It made me unhappy when built binaries were copied to the Windows target.

FIXME: Could we just remove the target property VERSION in add_llvm_executable() ?

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@241403 91177308-0d34-0410-b5e6-96231b3b80d8

tools/driver/CMakeLists.txt

@@ -38,7 +38,11 @@ target_link_libraries(clang
   clangFrontendTool
   )
 
-set_target_properties(clang PROPERTIES VERSION ${CLANG_EXECUTABLE_VERSION})
+if(WIN32 AND NOT CYGWIN)
+  # Prevent versioning if the buildhost is targeting for Win32.
+else()
+  set_target_properties(clang PROPERTIES VERSION ${CLANG_EXECUTABLE_VERSION})
+endif()
 
 # Support plugins.
 if(CLANG_PLUGIN_SUPPORT)