Exercise bootstrapping with the XCBuild codepath in build-using-self (#7253)

This codepath could regress since we previously didn't run it in our PR
testing.

With this change on macOS we always try to bootstrap SwiftPM with
XCBuild on top of the usual llbuild build and test run.

It does increase the time spent on the macOS self-hosted job, but that
job was already multiple times faster than our smoke test jobs, thus we
have enough leeway to make it longer with the benefit of better PR
testing.

Author: MaxDesiatov

Utilities/bootstrap

@@ -87,6 +87,10 @@ def add_global_args(parser):
 def add_build_args(parser):
     """Configures the parser with the arguments necessary for build-related actions."""
     add_global_args(parser)
+    parser.add_argument(
+        "--swift-build-path",
+        help="path to the prebuilt SwiftPM `swift-build` binary",
+        metavar="PATH")
     parser.add_argument(
         "--swiftc-path",
         help="path to the swift compiler",
@@ -154,7 +158,7 @@ def add_build_args(parser):
         default=[])
     parser.add_argument(
         "--cross-compile-config",
-        help="Swift flags to cross-compile SPM with itself")
+        help="Swift flags to cross-compile SwiftPM with itself")
 
 def add_test_args(parser):
     """Configures the parser with the arguments necessary for the test action."""
@@ -220,8 +224,9 @@ def parse_build_args(args):
 
     args.swiftc_path = get_swiftc_path(args)
     args.clang_path = get_tool_path(args, "clang")
-    args.cmake_path = get_tool_path(args, "cmake")
-    args.ninja_path = get_tool_path(args, "ninja")
+    if not args.skip_cmake_bootstrap:
+        args.cmake_path = get_tool_path(args, "cmake")
+        args.ninja_path = get_tool_path(args, "ninja")
     args.ar_path = get_tool_path(args, "ar")
     args.ranlib_path = get_tool_path(args, "ranlib")
     if args.cross_compile_hosts:
@@ -640,7 +645,7 @@ def build_swiftpm_with_swiftpm(args, integrated_swift_driver):
         swiftpm_args.append(os.path.join(args.bootstrap_dir, "bin/swift-bootstrap"))
     else:
         note("Building SwiftPM (with a prebuilt swift-build)")
-        swiftpm_args.append(os.path.join(os.path.split(args.swiftc_path)[0], "swift-build"))
+        swiftpm_args.append(args.swift_build_path or os.path.join(os.path.split(args.swiftc_path)[0], "swift-build"))
         swiftpm_args.append("--disable-sandbox")
 
         # Enforce resolved versions to avoid stray dependencies that aren't local.

Utilities/build-using-self

@@ -34,3 +34,13 @@ cd IntegrationTests
 # Perform package update in order to get the latest commits for the dependencies.
 swift package update
 $SWIFTPM_BIN_DIR/swift-test --parallel
+
+if [ "$(uname)" == "Darwin" ]; then
+  cd ..
+  echo "Current working directory is ${PWD}"
+  echo "Bootstrapping with the XCBuild codepath..."
+  ./Utilities/bootstrap build --release \
+    --cross-compile-hosts macosx-arm64 \
+    --skip-cmake-bootstrap \
+    --swift-build-path "${SWIFTPM_BIN_DIR}/swift-build"
+fi