Be smarter about Pch.[h|cpp] files

As pointed out in #225, Pch.cpp looks suspiciously like a garbage file
when precompiled headers are disabled in cmake. To solve that, I have
changed the precompiled header function to add the Pch source files only
when pch is enabled. This should prevent future accidents.

Sources/Plasma/FeatureLib/pfPython/CMakeLists.txt

@@ -19,7 +19,6 @@ set(pfPython_SOURCES
     cyParticleSys.cpp
     cyPhysics.cpp
     cyPythonInterface.cpp
-    Pch.cpp
     plPythonFileMod.cpp
     plPythonPack.cpp
     plPythonSDLModifier.cpp
@@ -105,7 +104,6 @@ set(pfPython_HEADERS
     cyParticleSys.h
     cyPhysics.h
     cyPythonInterface.h
-    Pch.h
     pfPythonCreatable.h
     plPythonFileMod.h
     plPythonHelpers.h
@@ -340,7 +338,7 @@ set(pfPython_GAMES
     ${pfPython_VSYNC}
 )
 
-use_precompiled_header(Pch.h Pch.cpp)
+use_precompiled_header(Pch.h Pch.cpp pfPython_HEADERS pfPython_SOURCES)
 add_library(pfPython STATIC ${pfPython_SOURCES} ${pfPython_HEADERS} ${pfPython_GLUE} ${pfPython_GAME_GLUE} ${pfPython_GAMES})
 
 source_group("Source Files" FILES ${pfPython_SOURCES})

cmake/PrecompiledHeader.cmake

@@ -8,7 +8,7 @@ if(PCH_SUPPORTED)
     option(PLASMA_USE_PCH "Enable precompiled headers?" ON)
 endif(PCH_SUPPORTED)
 
-macro(use_precompiled_header PrecompiledHeader PrecompiledSource)
+function(use_precompiled_header PrecompiledHeader PrecompiledSource Headers Sources)
     if(PLASMA_USE_PCH)
         if(MSVC)
             get_filename_component(PrecompiledBasename ${PrecompiledHeader} NAME_WE)
@@ -19,5 +19,10 @@ macro(use_precompiled_header PrecompiledHeader PrecompiledSource)
             add_definitions(/FI"${PrecompiledHeader}")
             set_source_files_properties(${PrecompiledSource} PROPERTIES COMPILE_FLAGS "/Yc\"${PrecompiledHeader}\"")
         endif(MSVC)
+
+        # Add the Pch.[h|cpp] to the appropriate sets
+        # OT: This has to be the oddest thing I've ever written =/
+        set(${Headers} ${${Headers}} ${PrecompiledHeader} PARENT_SCOPE)
+        set(${Sources} ${${Sources}} ${PrecompiledSource} PARENT_SCOPE)
     endif(PLASMA_USE_PCH)
-endmacro(use_precompiled_header)
+endfunction(use_precompiled_header)