Support cross compilation in macOS toolchain builds (#62306)

Updates the build script used in SwiftCI for building the `docc`
executable as part of Swift.org toolchains to support cross compilation.

Currently the `docc` executable included in the otherwise universal
macOS toolchain only supports x86_64. This resolves the issue.

Resolves rdar://102870094
Closes swiftlang/swift-docc#433

Author: ethan-kusters

utils/swift_build_support/swift_build_support/products/swiftdocc.py

@@ -64,6 +64,13 @@ def run_build_script_helper(self, action, host_target, additional_params=[]):
             '--build-dir', self.build_dir,
             '--multiroot-data-file', MULTIROOT_DATA_FILE_PATH,
         ]
+
+        # Pass Cross compile host info
+        if self.has_cross_compile_hosts() and self.is_darwin_host(host_target):
+            helper_cmd += ['--cross-compile-hosts']
+            for cross_compile_host in self.args.cross_compile_hosts:
+                helper_cmd += [cross_compile_host]
+
         if action != 'install':
             helper_cmd.extend([
                 # There might have been a Package.resolved created by other builds