[build] Support cross-compilation of swift-format

This should build swift-format as a fat binary containing both an x86_64 and an arm64 slice in the open source toolchains.

rdar://121326143

Author: ahoppen

utils/swift_build_support/swift_build_support/products/swiftformat.py

@@ -27,6 +27,7 @@
 from . import swiftsyntax
 from . import xctest
 from .. import shell
+from .. import targets
 
 
 class SwiftFormat(product.Product):
@@ -57,8 +58,6 @@ def run_build_script_helper(self, action, host_target, additional_params=[]):
         script_path = os.path.join(
             self.source_dir, 'build-script-helper.py')
 
-        install_destdir = self.host_install_destdir(host_target)
-
         helper_cmd = [
             script_path,
             action,
@@ -71,9 +70,33 @@ def run_build_script_helper(self, action, host_target, additional_params=[]):
             # reset the dependencies to be local.
             '--update'
         ]
-        helper_cmd.extend([
-            '--prefix', install_destdir + self.args.install_prefix
-        ])
+
+        install_destdir = self.host_install_destdir(host_target)
+        toolchain_path = self.native_toolchain_path(host_target)
+
+        # Pass Cross compile host info unless we're testing.
+        # It doesn't make sense to run tests of the cross compile host.
+        if self.has_cross_compile_hosts() and action != 'test':
+            if self.is_darwin_host(host_target):
+                if len(self.args.cross_compile_hosts) != 1:
+                    raise RuntimeError("Cross-Compiling swift-format to multiple " +
+                                       "targets is not supported")
+                helper_cmd += ['--cross-compile-host', self.args.cross_compile_hosts[0]]
+            elif self.is_cross_compile_target(host_target):
+                helper_cmd.extend(['--cross-compile-host', host_target])
+                build_toolchain_path = install_destdir + self.args.install_prefix
+                resource_dir = f'{build_toolchain_path}/lib/swift'
+                cross_compile_config = targets.StdlibDeploymentTarget \
+                    .get_target_for_name(host_target) \
+                    .platform \
+                    .swiftpm_config(
+                        self.args,
+                        output_dir=build_toolchain_path,
+                        swift_toolchain=toolchain_path,
+                        resource_path=resource_dir
+                    )
+                helper_cmd += ['--cross-compile-config', cross_compile_config]
+
         if self.args.verbose_build:
             helper_cmd.append('--verbose')
         helper_cmd.extend(additional_params)
@@ -139,7 +162,12 @@ def should_install(self, host_target):
         return self.args.install_swiftformat
 
     def install(self, host_target):
-        self.run_build_script_helper('install', host_target)
+        install_destdir = self.host_install_destdir(host_target)
+        self.run_build_script_helper(
+            'install',
+            host_target,
+            additional_params=['--prefix', install_destdir + self.args.install_prefix]
+        )
 
     @classmethod
     def get_dependencies(cls):