[build] Replace SWIFT_CROSS_COMPILING with SWIFT_PREBUILT_CLANG

Author: finagolfin

CMakeLists.txt

@@ -481,12 +481,6 @@ if(SWIFT_PATH_TO_CMARK_BUILD)
 endif()
 message(STATUS "")
 
-if("${SWIFT_NATIVE_LLVM_TOOLS_PATH}" STREQUAL "")
-  set(SWIFT_CROSS_COMPILING FALSE)
-else()
-  set(SWIFT_CROSS_COMPILING TRUE)
-endif()
-
 # Check if a prebuilt clang path was passed in, as this variable will be
 # assigned if not, in SwiftSharedCMakeConfig.
 if("${SWIFT_NATIVE_CLANG_TOOLS_PATH}" STREQUAL "")

cmake/modules/SwiftSharedCMakeConfig.cmake

@@ -58,7 +58,7 @@ macro(swift_common_standalone_build_config_llvm product)
     fix_imported_targets_for_xcode("${LLVM_EXPORTED_TARGETS}")
   endif()
 
-  if(NOT CMAKE_CROSSCOMPILING AND NOT SWIFT_CROSS_COMPILING)
+  if(NOT CMAKE_CROSSCOMPILING)
     set(${product}_NATIVE_LLVM_TOOLS_PATH "${LLVM_TOOLS_BINARY_DIR}")
   endif()
 
@@ -159,7 +159,7 @@ endmacro()
 macro(swift_common_standalone_build_config_clang product)
   find_package(Clang CONFIG REQUIRED NO_DEFAULT_PATH NO_CMAKE_FIND_ROOT_PATH)
 
-  if (NOT CMAKE_CROSSCOMPILING)
+  if (NOT CMAKE_CROSSCOMPILING AND NOT SWIFT_PREBUILT_CLANG)
     set(${product}_NATIVE_CLANG_TOOLS_PATH "${LLVM_TOOLS_BINARY_DIR}")
   endif()