llvm-rc: Enable preprocessing if CMAKE_RC_COMPILER_INIT is an absolute path

`CMAKE_RC_COMPILER_INIT` and `CMAKE_RC_COMPILER` can be set by user,
for example `llvm-rc-10` and `D:\LLVM\bin\llvm-rc.exe`.

Modules/Platform/Windows-Clang.cmake

@@ -134,7 +134,7 @@ if("x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC"
     include(Platform/Windows-MSVC)
 
     # Feed the preprocessed rc file to llvm-rc
-    if(CMAKE_RC_COMPILER_INIT STREQUAL "llvm-rc")
+    if(CMAKE_RC_COMPILER_INIT MATCHES "llvm-rc")
       if(DEFINED CMAKE_C_COMPILER_ID)
         set(CMAKE_RC_PREPROCESSOR CMAKE_C_COMPILER)
       elseif(DEFINED CMAKE_CXX_COMPILER_ID)