build: simplify source file handling for sourcekitdAPI

Avoid unnecessary list handling for the sources for sourcekitdAPI,
inline the single use of the list and appending of the sources.

Author: compnerd

tools/SourceKit/tools/sourcekitd/lib/API/CMakeLists.txt

@@ -1,5 +1,8 @@
+set(LLVM_OPTIONAL_SOURCES
+  sourcekitdAPI-XPC.cpp
+  sourcekitdAPI-InProc.cpp)
 
-set(sourcekitdAPI_sources
+add_sourcekit_library(sourcekitdAPI
   CodeCompletionResultsArray.cpp
   CompactArray.cpp
   DocStructureArray.cpp
@@ -9,22 +12,14 @@ set(sourcekitdAPI_sources
   sourcekitdAPI-Common.cpp
   TokenAnnotationsArray.cpp
   ExpressionTypeArray.cpp
+  LINK_LIBS
+      SourceKitSupport SourceKitSwiftLang
 )
 
-set(sourcekitdAPI_Darwin_sources
-  sourcekitdAPI-XPC.cpp)
-set(sourcekitdAPI_NonDarwin_InProc_sources
-  sourcekitdAPI-InProc.cpp)
-set(LLVM_OPTIONAL_SOURCES ${sourcekitdAPI_Darwin_sources} ${sourcekitdAPI_NonDarwin_InProc_sources})
-
 if(APPLE AND HAVE_XPC_H)
-  list(APPEND sourcekitdAPI_sources ${sourcekitdAPI_Darwin_sources})
+  target_sources(sourcekitdAPI PRIVATE
+    sourcekitdAPI-XPC.cpp)
 elseif(SWIFT_SOURCEKIT_USE_INPROC_LIBRARY)
-  list(APPEND sourcekitdAPI_sources ${sourcekitdAPI_NonDarwin_InProc_sources})
+  target_sources(sourcekitdAPI PRIVATE
+    sourcekitdAPI-InProc.cpp)
 endif()
-
-add_sourcekit_library(sourcekitdAPI
-  ${sourcekitdAPI_sources}
-  LINK_LIBS
-      SourceKitSupport SourceKitSwiftLang
-)