SourceKit: inline single-use variable (NFC)

Inline the unnecessary use of the variable for creating the
SourceKitSupport library.

Author: compnerd

tools/SourceKit/lib/Support/CMakeLists.txt

@@ -1,15 +1,11 @@
-set(SourceKitSupport_sources
+add_sourcekit_library(SourceKitSupport
   Concurrency-libdispatch.cpp
   FuzzyStringMatcher.cpp
   Logging.cpp
   ImmutableTextBuffer.cpp
   ThreadSafeRefCntPtr.cpp
   Tracing.cpp
   UIDRegistry.cpp
-)
-
-add_sourcekit_library(SourceKitSupport
-  ${SourceKitSupport_sources}
   LINK_LIBS swiftBasic swiftSyntax clangBasic clangRewrite
 )
 if(SWIFT_NEED_EXPLICIT_LIBDISPATCH)