msvs: Add support for Windows on Arm

Cherry-pick of refack/GYP3#33, supersedes
nodejs#1678 until GYP3 is merged.

`npm test` passes

Change-Id: I2b1e1e03e378b4812d34afa527087793864d1576

gyp/pylib/gyp/MSVSSettings.py

@@ -973,7 +973,9 @@ def _ValidateSettings(validators, settings, stderr):
       _Enumeration(['NotSet',
                     'Win32',  # /env win32
                     'Itanium',  # /env ia64
-                    'X64']))  # /env x64
+                    'X64',  # /env x64
+                    'ARM64',  # /env arm64
+                    ]))
 _Same(_midl, 'EnableErrorChecks',
       _Enumeration(['EnableCustom',
                     'None',  # /error none

gyp/pylib/gyp/generator/msvs.py

@@ -1887,6 +1887,8 @@ def _InitNinjaFlavor(params, target_list, target_dicts):
       configuration = '$(Configuration)'
       if params.get('target_arch') == 'x64':
         configuration += '_x64'
+      if params.get('target_arch') == 'arm64':
+        configuration += '_arm64'
       spec['msvs_external_builder_out_dir'] = os.path.join(
           gyp.common.RelativePath(params['options'].toplevel_dir, gyp_dir),
           ninja_generator.ComputeOutputDir(params),

gyp/pylib/gyp/msvs_emulation.py

@@ -237,7 +237,11 @@ def GetExtension(self):
   def GetVSMacroEnv(self, base_to_build=None, config=None):
     """Get a dict of variables mapping internal VS macro names to their gyp
     equivalents."""
-    target_platform = 'Win32' if self.GetArch(config) == 'x86' else 'x64'
+    target_arch = self.GetArch(config)
+    if target_arch == 'x86':
+      target_platform = 'Win32'
+    else:
+      target_platform = target_arch
     target_name = self.spec.get('product_prefix', '') + \
         self.spec.get('product_name', self.spec['target_name'])
     target_dir = base_to_build + '\\' if base_to_build else ''
@@ -299,7 +303,7 @@ def GetArch(self, config):
     if not platform: # If no specific override, use the configuration's.
       platform = configuration_platform
     # Map from platform to architecture.
-    return {'Win32': 'x86', 'x64': 'x64'}.get(platform, 'x86')
+    return {'Win32': 'x86', 'x64': 'x64', 'ARM64': 'arm64'}.get(platform, 'x86')
 
   def _TargetConfig(self, config):
     """Returns the target-specific configuration."""
@@ -563,7 +567,10 @@ def GetLdflags(self, config, gyp_to_build_path, expand_special,
                           'VCLinkerTool', append=ldflags)
     self._GetDefFileAsLdflags(ldflags, gyp_to_build_path)
     ld('GenerateDebugInformation', map={'true': '/DEBUG'})
-    ld('TargetMachine', map={'1': 'X86', '17': 'X64', '3': 'ARM'},
+    # TODO: These 'map' values come from machineTypeOption enum,
+    # and does not have an official value for ARM64 in VS2017 (yet).
+    # It needs to verify the ARM64 value when machineTypeOption is updated.
+    ld('TargetMachine', map={'1': 'X86', '17': 'X64', '3': 'ARM', '18': 'ARM64'},
        prefix='/MACHINE:')
     ldflags.extend(self._GetAdditionalLibraryDirectories(
         'VCLinkerTool', config, gyp_to_build_path))
@@ -860,7 +867,9 @@ def midl(name, default=None):
                  ('iid', iid),
                  ('proxy', proxy)]
     # TODO(scottmg): Are there configuration settings to set these flags?
-    target_platform = 'win32' if self.GetArch(config) == 'x86' else 'x64'
+    target_platform = self.GetArch(config)
+    if target_platform == 'x86':
+      target_platform = 'win32'
     flags = ['/char', 'signed', '/env', target_platform, '/Oicf']
     return outdir, output, variables, flags
 

lib/configure.js

@@ -134,6 +134,9 @@ function configure (gyp, argv, callback) {
 
     // set the target_arch variable
     variables.target_arch = gyp.opts.arch || process.arch || 'ia32'
+    if (variables.target_arch == 'arm64') {
+      defaults['msvs_configuration_platform'] = 'ARM64'
+    }
 
     // set the node development directory
     variables.nodedir = nodeDir