adjust run_tests_matrix.py windows portability suites

tools/run_tests/run_tests_matrix.py

@@ -209,12 +209,11 @@ def _create_portability_test_jobs(extra_args=[], inner_jobs=_DEFAULT_INNER_JOBS)
                                 extra_args=extra_args,
                                 inner_jobs=inner_jobs)
 
-  # portability C on Windows
-  for arch in ['x86', 'x64']:
+  # portability C on Windows 64-bit (x86 is the default)
   test_jobs += _generate_jobs(languages=['c'],
                               configs=['dbg'],
                               platforms=['windows'],
-                                arch=arch,
+                              arch='x64',
                               compiler='default',
                               labels=['portability', 'corelang'],
                               extra_args=extra_args,
@@ -231,6 +230,17 @@ def _create_portability_test_jobs(extra_args=[], inner_jobs=_DEFAULT_INNER_JOBS)
                               extra_args=extra_args + ['--build_only'],
                               inner_jobs=inner_jobs)
 
+  # portability C and C++ on Windows using VS2017 (build only)
+  # TODO(jtattermusch): some of the tests are failing, so we force --build_only
+  test_jobs += _generate_jobs(languages=['c', 'c++'],
+                              configs=['dbg'],
+                              platforms=['windows'],
+                              arch='x64',
+                              compiler='cmake_vs2017',
+                              labels=['portability', 'corelang'],
+                              extra_args=extra_args + ['--build_only'],
+                              inner_jobs=inner_jobs)
+
   # C and C++ with the c-ares DNS resolver on Linux
   test_jobs += _generate_jobs(languages=['c', 'c++'],
                               configs=['dbg'], platforms=['linux'],