[build-script] XCTest CI builds on OS X

Fix the OS X XCTest CI preset:

1. Installation of XCTest isn't supported on OS X. After all, the
   library is meant to be used on Linux, and not intended to be used or
   installed on OS X. Therefore, no longer pass an `INSTALL_PATH` to the
   `xcodebuild` invocation on OS X.
2. `xcodebuild` expects `swift-stdlib-tool` to be present in the same
   directory as the `SWIFT_EXEC` it's given. Re-use some shellscript
   from the toolchain installation script to copy the stdlib-tool
   substitute.

This allows the XCTest CI to work on all platforms.

Author: modocache

utils/build-script-impl

@@ -837,6 +837,15 @@ function cmake_needs_to_specify_standard_computed_defaults() {
     fi
 }
 
+function copy_swift_stdlib_tool_substitute() {
+    if [ ! -f "$1" ] ; then
+        echo "--- Copy swift-stdlib-tool ---"
+        set -x
+        cp "${SWIFT_SOURCE_DIR}/utils/swift-stdlib-tool-substitute" "$1"
+        { set +x; } 2>/dev/null
+    fi
+}
+
 # A list of deployment targets to cross-compile the Swift host tools for.
 # We can't run the resulting binaries on the build machine.
 CROSS_TOOLS_DEPLOYMENT_TARGETS=()
@@ -1931,16 +1940,23 @@ for deployment_target in "${HOST_TARGET}" "${CROSS_TOOLS_DEPLOYMENT_TARGETS[@]}"
                 SWIFTC_BIN="$(build_directory_bin ${deployment_target} swift)/swiftc"
                 XCTEST_BUILD_DIR=$(build_directory ${deployment_target} xctest)
                 if [[ "$(uname -s)" == "Darwin" ]] ; then
+                    # xcodebuild requires swift-stdlib-tool to build a Swift
+                    # framework. This is normally present when building XCTest
+                    # via a packaged .xctoolchain, but here we are using the
+                    # swiftc that was just built--no toolchain exists yet. As a
+                    # result, we must copy swift-stdlib-tool ourselves.
+                    copy_swift_stdlib_tool_substitute "$(build_directory_bin ${deployment_target} swift)/swift-stdlib-tool"
+
+                    # The Linux build places build products in the
+                    # XCTEST_BUILD_DIR. This, and installation of XCTest in
+                    # general, is not supported on OS X.
                     set -x
                     xcodebuild \
                         -workspace "${XCTEST_SOURCE_DIR}"/XCTest.xcworkspace \
                         -scheme SwiftXCTest \
                         SWIFT_EXEC="${SWIFTC_BIN}" \
                         SWIFT_LINK_OBJC_RUNTIME=YES \
-                        SKIP_INSTALL=NO \
-                        DEPLOYMENT_LOCATION=YES \
-                        DSTROOT="${XCTEST_BUILD_DIR}" \
-                        INSTALL_PATH="/"
+                        DSTROOT="${XCTEST_BUILD_DIR}"
                     { set +x; } 2>/dev/null
                 else
                     FOUNDATION_BUILD_DIR=$(build_directory ${deployment_target} foundation)
@@ -2529,10 +2545,7 @@ if [[ "${INSTALLABLE_PACKAGE}" ]] ; then
     echo "--- Creating installable package ---"
     echo "-- Package file: ${INSTALLABLE_PACKAGE} --"
     if [[ "$(uname -s)" == "Darwin" ]] ; then
-      if [ ! -f "${INSTALL_DESTDIR}/${INSTALL_PREFIX}/bin/swift-stdlib-tool" ] ; then
-        echo "--- Copy swift-stdlib-tool ---"
-        cp "${SWIFT_SOURCE_DIR}/utils/swift-stdlib-tool-substitute" "${INSTALL_DESTDIR}/${INSTALL_PREFIX}/bin/swift-stdlib-tool"
-      fi
+      copy_swift_stdlib_tool_substitute "${INSTALL_DESTDIR}/${INSTALL_PREFIX}/bin/swift-stdlib-tool"
 
       # Create plist for xctoolchain.
       echo "-- Create Info.plist --"