fixes VCTargetsPath in windows build.

Author: kdschlosser

builder/windows.py

@@ -58,6 +58,22 @@ def build_commands(_, extra_args, script_dir, lv_cflags, board):
         env = pyMSVC.setup_environment()
         print(env)
 
+        for key in os.environ.keys():
+            if 'COMNTOOLS' in key:
+                version = key.replace('COMNTOOLS', '').replace('VS', '')
+                break
+        else:
+            print(os.environ)
+            raise RuntimeError('unable to locate common tools version')
+
+        version = 'v' + version
+
+        msbuild_path = env.visual_c.msbuild_path.lower()
+        msbuild_path = msbuild_path.split('msbuild', 1)[0][:-1]
+
+        VCTargetsPath = os.path.join(msbuild_path, 'Msbuild', 'Microsoft', 'VC', version)
+        os.environ['VCTargetsPath'] = VCTargetsPath
+
         mpy_cross_cmd.extend([
             'msbuild',
             'lib/micropython/mpy-cross/mpy-cross.vcxproj'