[CMake] Make sure the host tools are being built before setting the bootstrapping mode on Unix platforms

Author: finagolfin

CMakeLists.txt

@@ -870,7 +870,7 @@ elseif(BOOTSTRAPPING_MODE STREQUAL "HOSTTOOLS" OR SWIFT_BUILD_SWIFT_SYNTAX)
   set(SWIFT_EXEC_FOR_SWIFT_MODULES "${CMAKE_Swift_COMPILER}")
 endif()
 
-if(SWIFT_BUILD_SWIFT_SYNTAX)
+if(SWIFT_INCLUDE_TOOLS AND SWIFT_BUILD_SWIFT_SYNTAX)
   # Only "HOSTTOOLS" is supported in Linux when Swift parser integration is enabled.
   if(SWIFT_HOST_VARIANT_SDK MATCHES "LINUX|OPENBSD|FREEBSD" AND NOT BOOTSTRAPPING_MODE STREQUAL "HOSTTOOLS")
     message(WARNING "Force setting BOOTSTRAPPING=HOSTTOOLS because Swift parser integration is enabled")