Use arm64 MSVC on arm64 Windows

distutils/_msvccompiler.py

@@ -33,7 +33,7 @@
     LibError,
     LinkError,
 )
-from .util import get_platform
+from .util import get_host_platform, get_platform
 
 
 def _find_vc2015():
@@ -178,15 +178,24 @@ def _find_exe(exe, paths=None):
     return exe
 
 
-# A map keyed by get_platform() return values to values accepted by
-# 'vcvarsall.bat'. Always cross-compile from x86 to work with the
-# lighter-weight MSVC installs that do not include native 64-bit tools.
-PLAT_TO_VCVARS = {
-    'win32': 'x86',
-    'win-amd64': 'x86_amd64',
-    'win-arm32': 'x86_arm',
-    'win-arm64': 'x86_arm64',
-}
+if get_host_platform() == "win-arm64":
+    # Use the native MSVC host if the host platform would need expensive
+    # emulation for x86.
+    PLAT_TO_VCVARS = {
+        'win32': 'arm64_x86',
+        'win-amd64': 'arm64_amd64',
+        'win-arm32': 'arm64_arm',
+        'win-arm64': 'arm64',
+    }
+else:
+    # Always cross-compile from x86 to work with the lighter-weight MSVC
+    # installs that do not include native 64-bit tools.
+    PLAT_TO_VCVARS = {
+        'win32': 'x86',
+        'win-amd64': 'x86_amd64',
+        'win-arm32': 'x86_arm',
+        'win-arm64': 'x86_arm64',
+    }
 
 
 class MSVCCompiler(CCompiler):