fix a linker error on the benchmark bot

It looks like removing this dependency (#19798) caused the linker error on https://ci.swift.org/view/Pull%20Request/job/swift-PR-osx-perf/

Author: eeckstein

tools/SourceKit/tools/swift-lang/CMakeLists.txt

@@ -13,6 +13,7 @@ if(NOT SWIFT_SOURCEKIT_USE_INPROC_LIBRARY AND SWIFT_BUILD_STDLIB)
     UIDs.swift.gyb
 
     DEPENDS ${DEPENDS_LIST}
+    SWIFT_MODULE_DEPENDS_OSX Darwin
     PRIVATE_LINK_LIBRARIES ${SOURCEKITD_LINK_LIBS}
     SWIFT_COMPILE_FLAGS ${EXTRA_COMPILE_FLAGS}
     INSTALL_IN_COMPONENT ${INSTALLED_COMP}