diff --git a/lldb/test/Shell/helper/build.py b/lldb/test/Shell/helper/build.py
--- a/lldb/test/Shell/helper/build.py
+++ b/lldb/test/Shell/helper/build.py
@@ -277,7 +277,10 @@
     def __init__(self, toolchain_type, args):
         Builder.__init__(self, toolchain_type, args, '.obj')
 
-        self.msvc_arch_str = 'x86' if self.arch == '32' else 'x64'
+        if os.getenv('PLATFORM') == 'arm64':
+            self.msvc_arch_str = 'arm' if self.arch == '32' else 'arm64'
+        else:
+            self.msvc_arch_str = 'x86' if self.arch == '32' else 'x64'
 
         if toolchain_type == 'msvc':
             # Make sure we're using the appropriate toolchain for the desired
diff --git a/llvm/utils/lit/lit/llvm/config.py b/llvm/utils/lit/lit/llvm/config.py
--- a/llvm/utils/lit/lit/llvm/config.py
+++ b/llvm/utils/lit/lit/llvm/config.py
@@ -38,7 +38,7 @@
             # Many tools behave strangely if these environment variables aren't
             # set.
             self.with_system_environment(
-                ['SystemDrive', 'SystemRoot', 'TEMP', 'TMP'])
+                ['SystemDrive', 'SystemRoot', 'TEMP', 'TMP', 'PLATFORM'])
             self.use_lit_shell = True
 
             global lit_path_displayed