feat: Windows ARM64 target architecture support (#331)

* feat: ARM64 target architecture support

Extend the MSVC toolchain integration to support Windows ARM64 targets.

(I know very little about gyp, so these changes may be a bit rough. They were enough to get NSS building on Windows 11/ARM in CI via mozilla/neqo#2591. Please let me know if anything needs changing!)

* Update pylib/gyp/MSVSVersion.py

Co-authored-by: Christian Clauss <cclauss@me.com>

---------

Co-authored-by: Christian Clauss <cclauss@me.com>

Author: larseggert

pylib/gyp/MSVSVersion.py

@@ -87,7 +87,7 @@ def DefaultToolset(self):
     def _SetupScriptInternal(self, target_arch):
         """Returns a command (with arguments) to be used to set up the
         environment."""
-        assert target_arch in ("x86", "x64"), "target_arch not supported"
+        assert target_arch in ("x86", "x64", "arm64"), "target_arch not supported"
         # If WindowsSDKDir is set and SetEnv.Cmd exists then we are using the
         # depot_tools build tools and should run SetEnv.Cmd to set up the
         # environment. The check for WindowsSDKDir alone is not sufficient because
@@ -109,8 +109,16 @@ def _SetupScriptInternal(self, target_arch):
             )
 
             # Always use a native executable, cross-compiling if necessary.
-            host_arch = "amd64" if is_host_arch_x64 else "x86"
-            msvc_target_arch = "amd64" if target_arch == "x64" else "x86"
+            host_arch = (
+                "amd64"
+                if is_host_arch_x64
+                else (
+                    "arm64"
+                    if os.environ.get("PROCESSOR_ARCHITECTURE") == "ARM64"
+                    else "x86"
+                )
+            )
+            msvc_target_arch = {"x64": "amd64"}.get(target_arch, target_arch)
             arg = host_arch
             if host_arch != msvc_target_arch:
                 arg += "_" + msvc_target_arch

pylib/gyp/generator/ninja.py

@@ -246,7 +246,7 @@ def __init__(
         if flavor == "win":
             # See docstring of msvs_emulation.GenerateEnvironmentFiles().
             self.win_env = {}
-            for arch in ("x86", "x64"):
+            for arch in ("x86", "x64", "arm64"):
                 self.win_env[arch] = "environment." + arch
 
         # Relative path from build output dir to base dir.
@@ -2339,6 +2339,7 @@ def GenerateOutputForConfig(target_list, target_dicts, data, params, config_name
         master_ninja.variable("rc", "rc.exe")
         master_ninja.variable("ml_x86", "ml.exe")
         master_ninja.variable("ml_x64", "ml64.exe")
+        master_ninja.variable("ml_arm64", "armasm64.exe")
         master_ninja.variable("mt", "mt.exe")
     else:
         master_ninja.variable("ld", CommandWithWrapper("LINK", wrappers, ld))

pylib/gyp/msvs_emulation.py

@@ -1174,7 +1174,7 @@ def GenerateEnvironmentFiles(
     meet your requirement (e.g. for custom toolchains), you can pass
     "-G ninja_use_custom_environment_files" to the gyp to suppress file
     generation and use custom environment files prepared by yourself."""
-    archs = ("x86", "x64")
+    archs = ("x86", "x64", "arm64")
     if generator_flags.get("ninja_use_custom_environment_files", 0):
         cl_paths = {}
         for arch in archs: