bpo-37201: fix test_distutils failures for Windows ARM64 (GH-13902)

diff --git a/Lib/distutils/_msvccompiler.py b/Lib/distutils/_msvccompiler.py
index c7ac3f0..6e14f33 100644
--- a/Lib/distutils/_msvccompiler.py
+++ b/Lib/distutils/_msvccompiler.py
@@ -93,6 +93,7 @@
     'x86' : 'x86',
     'x86_amd64' : 'x64',
     'x86_arm' : 'arm',
+    'x86_arm64' : 'arm64'
 }
 
 def _find_vcvarsall(plat_spec):
@@ -190,6 +191,7 @@
     'win32' : 'x86',
     'win-amd64' : 'x86_amd64',
     'win-arm32' : 'x86_arm',
+    'win-arm64' : 'x86_arm64'
 }
 
 # A set containing the DLLs that are guaranteed to be available for