SourceKit: libdispatch swift requires swift stdlib

When building libdispatch for SourceKit, only enable the swift overlay
components if the swift standard library is being built.  This allows building
just the compiler and SourceKit.

Author: compnerd

tools/SourceKit/CMakeLists.txt

@@ -93,6 +93,12 @@ include_directories(BEFORE
 if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
   set(SOURCEKIT_DEFAULT_TARGET_SDK "LINUX")
   if(SWIFT_BUILD_SOURCEKIT)
+    if(SWIFT_BUILD_STDLIB)
+      set(SOURCEKIT_LIBDISPATCH_ENABLE_SWIFT YES)
+    else()
+      set(SOURCEKIT_LIBDISPATCH_ENABLE_SWIFT NO)
+    endif()
+
     include(ExternalProject)
     ExternalProject_Add(libdispatch
                         SOURCE_DIR
@@ -106,7 +112,7 @@ if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
                           -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
                           -DCMAKE_SWIFT_COMPILER=$<TARGET_FILE:swift>c
                           -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
-                          -DENABLE_SWIFT=YES
+                          -DENABLE_SWIFT=${SOURCEKIT_LIBDISPATCH_ENABLE_SWIFT}
                         BUILD_BYPRODUCTS
                           ${SWIFT_PATH_TO_LIBDISPATCH_BUILD}/src/${CMAKE_SHARED_LIBRARY_PREFIX}dispatch${CMAKE_SHARED_LIBRARY_SUFFIX}
                           ${SWIFT_PATH_TO_LIBDISPATCH_BUILD}/${CMAKE_STATIC_LIBRARY_PREFIX}BlocksRuntime${CMAKE_STATIC_LIBRARY_SUFFIX}
@@ -126,13 +132,16 @@ if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
     include_directories(AFTER
                           ${SWIFT_PATH_TO_LIBDISPATCH_SOURCE}/src/BlocksRuntime
                           ${SWIFT_PATH_TO_LIBDISPATCH_SOURCE})
-    add_dependencies(libdispatch
-                       swift
-                       copy_shim_headers
-                       swiftCore-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}
-                       swiftSwiftOnoneSupport-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}
-                       swiftCore-swiftmodule-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}
-                       swiftSwiftOnoneSupport-swiftmodule-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH})
+
+    if(SWIFT_BUILD_STDLIB)
+      add_dependencies(libdispatch
+                         swift
+                         copy_shim_headers
+                         swiftCore-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}
+                         swiftSwiftOnoneSupport-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}
+                         swiftCore-swiftmodule-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH}
+                         swiftSwiftOnoneSupport-swiftmodule-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH})
+    endif()
   endif()
 
   ExternalProject_Get_Property(libdispatch install_dir)
@@ -142,9 +151,13 @@ if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
                           IMPORTED_LOCATION
                             ${SWIFT_PATH_TO_LIBDISPATCH_BUILD}/src/${CMAKE_SHARED_LIBRARY_PREFIX}dispatch${CMAKE_SHARED_LIBRARY_SUFFIX}
                           INTERFACE_INCLUDE_DIRECTORIES
-                            ${install_dir}/include
-                          IMPORTED_LINK_INTERFACE_LIBRARIES
-                            swiftCore-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH})
+                            ${install_dir}/include)
+  if(SWIFT_BUILD_STDLIB)
+    set_target_properties(dispatch
+                          PROPERTIES
+                            IMPORTED_LINK_INTERFACE_LIBRARIES
+                              swiftCore-${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_LIB_SUBDIR}-${SWIFT_HOST_VARIANT_ARCH})
+  endif()
 
   add_library(BlocksRuntime STATIC IMPORTED)
   set_target_properties(BlocksRuntime