Merge pull request #2690 from gottesmm/specify_compiler_rt_uses_llvm_external_project_mechanism

[build-script] When building compiler-rt, follow LLVM's lead by speci…

Author: gottesmm

utils/build-script-impl

@@ -527,6 +527,7 @@ function set_deployment_target_based_options() {
                 -DLLVM_HOST_TRIPLE:STRING="${llvm_host_triple}"
                 -DLLVM_ENABLE_LIBCXX:BOOL=TRUE
                 -DLLVM_TOOL_COMPILER_RT_BUILD:BOOL="$(false_true ${SKIP_COMPILER_RT})"
+                -DLLVM_BUILD_EXTERNAL_COMPILER_RT:BOOL="$(false_true ${SKIP_COMPILER_RT})"
                 -DCOMPILER_RT_ENABLE_IOS:BOOL=FALSE
                 -DCOMPILER_RT_ENABLE_WATCHOS:BOOL=FALSE
                 -DCOMPILER_RT_ENABLE_TVOS:BOOL=FALSE
@@ -1894,6 +1895,31 @@ for deployment_target in "${HOST_TARGET}" "${CROSS_COMPILE_TOOLS_DEPLOYMENT_TARG
             { set +x; } 2>/dev/null
         fi
 
+        # When we are building LLVM create symlinks to the c++ headers. We need
+        # to do this before building LLVM since compiler-rt depends on being
+        # built with the just built clang compiler. These are normally put into
+        # place during the cmake step of LLVM's build when libcxx is in
+        # tree... but we are not building llvm with libcxx in tree when we build
+        # swift. So we need to do configure's work here.
+        if [[ "${product}" == "llvm" ]]; then
+            # Find the location of the c++ header dir.
+            if [[ "$(uname -s)" == "Darwin" ]] ; then
+              HOST_CXX_DIR=$(dirname ${HOST_CXX})
+              HOST_CXX_HEADERS_DIR="$HOST_CXX_DIR/../../usr/include/c++"
+            else # Linux
+              HOST_CXX_HEADERS_DIR="/usr/include/c++"
+            fi
+
+            # Find the path in which the local clang build is expecting to find
+            # the c++ header files.
+            BUILT_CXX_INCLUDE_DIR="$llvm_build_dir/include"
+
+            echo "symlinking the system headers ($HOST_CXX_HEADERS_DIR) into the local clang build directory ($BUILT_CXX_INCLUDE_DIR)."
+            set -x
+            ln -s -f "$HOST_CXX_HEADERS_DIR" "$BUILT_CXX_INCLUDE_DIR"
+            { set +x; } 2>/dev/null
+        fi
+
         # Build.
         if [[ ! "${skip_build}" ]]; then
             if [[ "${CMAKE_GENERATOR}" == "Xcode" ]] ; then
@@ -1913,26 +1939,6 @@ for deployment_target in "${HOST_TARGET}" "${CROSS_COMPILE_TOOLS_DEPLOYMENT_TARG
             ${DISTCC_PUMP} "${CMAKE}" --build "${build_dir}" $(cmake_config_opt ${product}) -- "${BUILD_ARGS[@]}" ${build_targets[@]}
             { set +x; } 2>/dev/null
         fi
-
-        # When we are building LLVM create symlinks to the c++ headers.
-        if [[ "${product}" == "llvm" ]]; then
-            # Find the location of the c++ header dir.
-            if [[ "$(uname -s)" == "Darwin" ]] ; then
-              HOST_CXX_DIR=$(dirname ${HOST_CXX})
-              HOST_CXX_HEADERS_DIR="$HOST_CXX_DIR/../../usr/include/c++"
-            else # Linux
-              HOST_CXX_HEADERS_DIR="/usr/include/c++"
-            fi
-
-            # Find the path in which the local clang build is expecting to find
-            # the c++ header files.
-            BUILT_CXX_INCLUDE_DIR="$llvm_build_dir/include"
-
-            echo "symlinking the system headers ($HOST_CXX_HEADERS_DIR) into the local clang build directory ($BUILT_CXX_INCLUDE_DIR)."
-            set -x
-            ln -s -f "$HOST_CXX_HEADERS_DIR" "$BUILT_CXX_INCLUDE_DIR"
-            { set +x; } 2>/dev/null
-        fi
     done
 done
 # END OF BUILD PHASE