commit f84992addb0f7cd54c13762274e898f79d0b0631
Date: Sun, 8 Nov 2020 13:25:13 +0530
Subject: [build] Make it possible to actually build the stdlib with a
 prebuilt clang

diff --git a/swift/CMakeLists.txt b/swift/CMakeLists.txt
index 99937910af2b..2cec8d38a493 100644
--- a/swift/CMakeLists.txt
+++ b/swift/CMakeLists.txt
@@ -462,10 +462,12 @@ if(SWIFT_PATH_TO_CMARK_BUILD)
 endif()
 message(STATUS "")
 
-if("${SWIFT_NATIVE_LLVM_TOOLS_PATH}" STREQUAL "")
-  set(SWIFT_CROSS_COMPILING FALSE)
+# Check if a prebuilt clang path was passed in, as this variable will be
+# assigned if not, in SwiftSharedCMakeConfig.
+if("${SWIFT_NATIVE_CLANG_TOOLS_PATH}" STREQUAL "")
+  set(SWIFT_PREBUILT_CLANG FALSE)
 else()
-  set(SWIFT_CROSS_COMPILING TRUE)
+  set(SWIFT_PREBUILT_CLANG TRUE)
 endif()
 
 include(SwiftSharedCMakeConfig)
diff --git a/swift/cmake/modules/SwiftSharedCMakeConfig.cmake b/swift/cmake/modules/SwiftSharedCMakeConfig.cmake
index c4c15084fe9..9ee08656589 100644
--- a/swift/cmake/modules/SwiftSharedCMakeConfig.cmake
+++ b/swift/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()
 
diff --git a/swift/stdlib/cmake/modules/AddSwiftStdlib.cmake b/swift/stdlib/cmake/modules/AddSwiftStdlib.cmake
index 7a296b5807d5..ace3fb90370f 100644
--- a/swift/stdlib/cmake/modules/AddSwiftStdlib.cmake
+++ b/swift/stdlib/cmake/modules/AddSwiftStdlib.cmake
@@ -1653,7 +1653,8 @@ function(add_swift_target_library name)
     list(APPEND SWIFTLIB_SWIFT_COMPILE_FLAGS "-warn-implicit-overrides")
   endif()
 
-  if(NOT SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER AND NOT BUILD_STANDALONE)
+  if(NOT SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER AND NOT BUILD_STANDALONE AND
+     NOT SWIFT_PREBUILT_CLANG)
     list(APPEND SWIFTLIB_DEPENDS clang)
   endif()
 
diff --git a/swift/stdlib/public/SwiftShims/CMakeLists.txt b/swift/stdlib/public/SwiftShims/CMakeLists.txt
index 33c49a3f8861..8553f4f00b37 100644
--- a/swift/stdlib/public/SwiftShims/CMakeLists.txt
+++ b/swift/stdlib/public/SwiftShims/CMakeLists.txt
@@ -110,7 +110,8 @@ endif()
 # First extract the "version" used for Clang's resource directory.
 string(REGEX MATCH "[0-9]+\\.[0-9]+(\\.[0-9]+)?" CLANG_VERSION
   "${LLVM_PACKAGE_VERSION}")
-if(NOT SWIFT_INCLUDE_TOOLS AND SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER)
+if(NOT SWIFT_INCLUDE_TOOLS AND
+   (SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER OR SWIFT_PREBUILT_CLANG))
   if(SWIFT_COMPILER_IS_MSVC_LIKE)
     execute_process(COMMAND ${CMAKE_C_COMPILER} /clang:-print-resource-dir
       OUTPUT_VARIABLE clang_headers_location