commit 32d341e244d4a56185ed04c60542250b5b5047e9
Date:   Thu Jul 16 17:23:18 2020 +0530

    [build] extend support for building with a prebuilt toolchain to the corelibs and llbuild

diff --git a/swift/utils/build-script-impl b/swift/utils/build-script-impl
index 7f39ff97459..af310ec8cbf 100755
--- a/swift/utils/build-script-impl
+++ b/swift/utils/build-script-impl
@@ -1584,6 +1584,18 @@ for host in "${ALL_HOSTS[@]}"; do
         )
     fi
 
+    if [[ "${NATIVE_CLANG_TOOLS_PATH}" ]] ; then
+        CLANG_BIN="${NATIVE_CLANG_TOOLS_PATH}"
+    else
+        CLANG_BIN="$(build_directory_bin ${LOCAL_HOST} llvm)"
+    fi
+
+    if [[ "${NATIVE_SWIFT_TOOLS_PATH}" ]] ; then
+        SWIFTC_BIN="${NATIVE_SWIFT_TOOLS_PATH}/swiftc"
+    else
+        SWIFTC_BIN="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
+    fi
+
     for product in "${PRODUCTS[@]}"; do
         [[ $(should_execute_action "${host}-${product/_static}-build") ]] || continue
 
@@ -2022,7 +2034,7 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DCMAKE_C_FLAGS="$(llvm_c_flags ${host})"
                     -DCMAKE_CXX_FLAGS="$(llvm_c_flags ${host})"
                     -DCMAKE_BUILD_TYPE:STRING="${LLDB_BUILD_TYPE}"
-                    -DLLDB_SWIFTC:PATH="$(build_directory ${LOCAL_HOST} swift)/bin/swiftc"
+                    -DLLDB_SWIFTC:PATH=${SWIFTC_BIN}
                     -DLLDB_SWIFT_LIBS:PATH="$(build_directory ${LOCAL_HOST} swift)/lib/swift"
                     -DCMAKE_INSTALL_PREFIX:PATH="$(get_host_install_prefix ${host})"
                     -DLLDB_FRAMEWORK_INSTALL_DIR="$(get_host_install_prefix ${host})../System/Library/PrivateFrameworks"
@@ -2073,8 +2085,10 @@ for host in "${ALL_HOSTS[@]}"; do
                     "${llbuild_cmake_options[@]}"
 
                     -DCMAKE_BUILD_TYPE:STRING="${LLBUILD_BUILD_TYPE}"
+                    -DCMAKE_C_COMPILER:PATH="${CLANG_BIN}/clang"
+                    -DCMAKE_CXX_COMPILER:PATH="${CLANG_BIN}/clang++"
                     -DCMAKE_INSTALL_PREFIX:PATH="$(get_host_install_prefix ${host})"
-                    -DCMAKE_Swift_COMPILER:PATH="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
+                    -DCMAKE_Swift_COMPILER:PATH=${SWIFTC_BIN}
                     -DCMAKE_Swift_FLAGS:STRING="-module-cache-path \"${module_cache}\""
 
                     -DLLBUILD_ENABLE_ASSERTIONS:BOOL=$(true_false "${LLBUILD_ENABLE_ASSERTIONS}")
@@ -2082,7 +2096,7 @@ for host in "${ALL_HOSTS[@]}"; do
 
                     -DLIT_EXECUTABLE:PATH="${LLVM_SOURCE_DIR}/utils/lit/lit.py"
                     -DFILECHECK_EXECUTABLE:PATH="$(build_directory_bin ${LOCAL_HOST} llvm)/FileCheck"
-                    -DSWIFTC_EXECUTABLE:PATH="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
+                    -DSWIFTC_EXECUTABLE:PATH=${SWIFTC_BIN}
                     -DFOUNDATION_BUILD_DIR:PATH="$(build_directory ${host} foundation)"
                     -DLIBDISPATCH_BUILD_DIR:PATH="$(build_directory ${host} libdispatch)"
                     -DLIBDISPATCH_SOURCE_DIR:PATH="${LIBDISPATCH_SOURCE_DIR}"
@@ -2106,7 +2120,6 @@ for host in "${ALL_HOSTS[@]}"; do
                 fi
                 ;;
             xctest)
-                SWIFTC_BIN="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
                 XCTEST_BUILD_DIR=$(build_directory ${host} xctest)
                 FOUNDATION_BUILD_DIR=$(build_directory ${host} foundation)
                 SWIFT_BUILD_DIR=$(build_directory ${host} swift)
@@ -2144,14 +2157,12 @@ for host in "${ALL_HOSTS[@]}"; do
                   echo "Cleaning the XCTest build directory"
                   call rm -rf "${XCTEST_BUILD_DIR}"
 
-                  LLVM_BIN="$(build_directory_bin ${LOCAL_HOST} llvm)"
-
                   cmake_options=(
                     ${cmake_options[@]}
                     -DCMAKE_BUILD_TYPE:STRING="${XCTEST_BUILD_TYPE}"
-                    -DCMAKE_C_COMPILER:PATH="${LLVM_BIN}/clang"
-                    -DCMAKE_CXX_COMPILER:PATH="${LLVM_BIN}/clang++"
-                    -DCMAKE_Swift_COMPILER:PATH="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
+                    -DCMAKE_C_COMPILER:PATH="${CLANG_BIN}/clang"
+                    -DCMAKE_CXX_COMPILER:PATH="${CLANG_BIN}/clang++"
+                    -DCMAKE_Swift_COMPILER:PATH=${SWIFTC_BIN}
                     -DCMAKE_Swift_FLAGS:STRING="-module-cache-path \"${module_cache}\""
                     -DCMAKE_INSTALL_PREFIX:PATH="$(get_host_install_prefix ${host})"
                     -DCMAKE_INSTALL_LIBDIR:PATH="lib"
@@ -2163,7 +2174,7 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DXCTEST_PATH_TO_LIBDISPATCH_SOURCE:PATH=${LIBDISPATCH_SOURCE_DIR}
                     -DXCTEST_PATH_TO_LIBDISPATCH_BUILD:PATH=$(build_directory ${host} libdispatch)
                     -DXCTEST_PATH_TO_FOUNDATION_BUILD:PATH=${FOUNDATION_BUILD_DIR}
-                    -DCMAKE_SWIFT_COMPILER:PATH="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
+                    -DCMAKE_SWIFT_COMPILER:PATH=${SWIFTC_BIN}
                     -DCMAKE_PREFIX_PATH:PATH=$(build_directory ${host} llvm)
 
                     -DENABLE_TESTING=YES
@@ -2178,9 +2189,6 @@ for host in "${ALL_HOSTS[@]}"; do
                 # is not yet built at this point.
                 XCTEST_BUILD_DIR=$(build_directory ${host} xctest)
 
-                SWIFTC_BIN="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
-                LLVM_BIN="$(build_directory_bin ${LOCAL_HOST} llvm)"
-
                 if [[ ${host} == "macosx"* ]]; then
                     echo "Skipping Foundation on OS X -- use the Xcode project instead"
                     continue
@@ -2220,8 +2228,8 @@ for host in "${ALL_HOSTS[@]}"; do
                 cmake_options=(
                   ${cmake_options[@]}
                   -DCMAKE_BUILD_TYPE:STRING=${FOUNDATION_BUILD_TYPE}
-                  -DCMAKE_C_COMPILER:PATH=${LLVM_BIN}/clang
-                  -DCMAKE_CXX_COMPILER:PATH=${LLVM_BIN}/clang++
+                  -DCMAKE_C_COMPILER:PATH=${CLANG_BIN}/clang
+                  -DCMAKE_CXX_COMPILER:PATH=${CLANG_BIN}/clang++
                   -DCMAKE_SWIFT_COMPILER:PATH=${SWIFTC_BIN}
                   -DCMAKE_Swift_COMPILER:PATH=${SWIFTC_BIN}
                   -DCMAKE_Swift_FLAGS:STRING="-module-cache-path \"${module_cache}\""
@@ -2244,8 +2252,6 @@ for host in "${ALL_HOSTS[@]}"; do
             libdispatch|libdispatch_static)
                 LIBDISPATCH_BUILD_DIR=$(build_directory ${host} ${product})
                 SWIFT_BUILD_PATH="$(build_directory ${host} swift)"
-                SWIFTC_BIN="$(build_directory_bin ${LOCAL_HOST} swift)/swiftc"
-                LLVM_BIN="$(build_directory_bin ${LOCAL_HOST} llvm)"
 
                 case "${host}" in
                 macosx-*)
@@ -2264,8 +2270,8 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DENABLE_SWIFT=YES
                     ${cmake_options[@]}
                     -DCMAKE_BUILD_TYPE:STRING="${LIBDISPATCH_BUILD_TYPE}"
-                    -DCMAKE_C_COMPILER:PATH="${LLVM_BIN}/clang"
-                    -DCMAKE_CXX_COMPILER:PATH="${LLVM_BIN}/clang++"
+                    -DCMAKE_C_COMPILER:PATH="${CLANG_BIN}/clang"
+                    -DCMAKE_CXX_COMPILER:PATH="${CLANG_BIN}/clang++"
                     -DCMAKE_SWIFT_COMPILER:PATH="${SWIFTC_BIN}"
                     -DCMAKE_Swift_COMPILER:PATH="${SWIFTC_BIN}"
                     -DCMAKE_Swift_FLAGS:STRING="-module-cache-path \"${module_cache}\""