Use vswhere to detect Visual Studio 2017.

xenia-build

@@ -48,8 +48,9 @@ def main():
   # Grab Visual Studio version and execute shell to set up environment.
   if sys.platform == 'win32':
     vs_version = import_vs_environment()
-    if vs_version != 2015:
-      print('ERROR: Visual Studio 2015 not found!')
+    if vs_version == 0:
+      print('ERROR: Visual Studio not found!')
+      print('Visual Studio 2015 is the recommended version.')
       print('Ensure you have the VS140COMNTOOLS environment variable!')
       sys.exit(1)
       return
@@ -98,15 +99,23 @@ def import_vs_environment():
     A version such as 2015 or None if no VS is found.
   """
   version = 0
+
+  candidate_path = subprocess.check_output('third_party/vswhere/vswhere.exe -version "[15,)" -latest -format value -property installationPath', shell=False);
+  candidate_path = candidate_path.strip()
+
   tools_path = ''
-  if 'VS140COMNTOOLS' in os.environ:
+  if candidate_path:
+    tools_path = os.path.join(candidate_path, 'vc\\auxiliary\\build\\vcvarsall.bat')
+    if os.path.isfile(tools_path) and os.access(tools_path, os.X_OK):
+      version = 2017
+  if version == 0 and 'VS140COMNTOOLS' in os.environ:
     version = 2015
     tools_path = os.environ['VS140COMNTOOLS']
+    tools_path = os.path.join(tools_path, '..\\..\\vc\\vcvarsall.bat')
   if version == 0:
     return None
-  tools_path = os.path.join(tools_path, '..\\..\\vc\\vcvarsall.bat')
 
-  args = [tools_path, '&&', 'set']
+  args = [tools_path, 'x64', '&&', 'set']
   popen = subprocess.Popen(
       args, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
   variables, _ = popen.communicate()