[build] Don’t build swift-refactor if swift-syntax is not being built

This fixes a build issue for Android.

Author: ahoppen

tools/swift-refactor/CMakeLists.txt

@@ -1,3 +1,8 @@
+if (NOT SWIFT_BUILD_SWIFT_SYNTAX)
+  # swiftRefactoring requires SwiftIDEUtilsBriding, which isn't built if SWIFT_BUILD_SWIFT_SYNTAX is `NO`.
+  return()
+endif()
+
 add_swift_host_tool(swift-refactor
   swift-refactor.cpp
   SWIFT_COMPONENT tools