Launch at least some Windows tests on CI (#201)

All custom tools (MS Visual Studio) information goes into
windows_commands.bzl

.bazelci/config.yaml

@@ -9,3 +9,6 @@ platforms:
   macos:
     test_targets:
     - "@rules_foreign_cc_tests//:cmake_tests"
+  windows:
+    test_targets:
+    - "@rules_foreign_cc_tests//:win_tests"

examples/BUILD

@@ -43,10 +43,10 @@ test_suite(
     name = "win_tests",
     tags = ["windows"],
     tests = tests + [
-        "//cmake_synthetic:test_libs",
-        "//configure_gnuplot:configure_libgd_tests",
+#        "//cmake_synthetic:test_libs",
+#        "//configure_gnuplot:configure_libgd_tests",
         "//cmake_hello_world_lib/static:test_hello_ninja",
-        "//cmake_hello_world_lib/static:test_hello_nmake",
+#        "//cmake_hello_world_lib/static:test_hello_nmake",
     ],
 )
 

examples/cmake_hello_world_lib/static/BUILD

@@ -18,7 +18,7 @@ cmake_external(
 
 cmake_external(
     name = "libhello_win",
-    cmake_options = ["-G \"Visual Studio 15 2017 Win64\""],
+    cmake_options = ["-G \"Visual Studio 14 2015 Win64\""],
     generate_crosstool_file = True,
     lib_name = "libhello",
     lib_source = ":srcs",

tools/build_defs/cmake_script.bzl

@@ -2,8 +2,6 @@
 
 load(":cc_toolchain_util.bzl", "absolutize_path_in_str")
 
-CMAKE_COMMAND = "cmake"
-
 def create_cmake_script(
         workspace_name,
         target_os,
@@ -267,6 +265,8 @@ def _tail_if_starts_with(str, start):
     return None
 
 def _absolutize(workspace_name, text, force = False):
+    if text.strip(" ").startswith("C:") or text.strip(" ").startswith("c:"):
+        return text
     return absolutize_path_in_str(workspace_name, "$EXT_BUILD_ROOT/", text, force)
 
 def _join_flags_list(workspace_name, flags):

tools/build_defs/shell_toolchain/toolchains/impl/windows_commands.bzl

@@ -104,6 +104,10 @@ fi
 export MSYS_NO_PATHCONV=1
 export MSYS2_ARG_CONV_EXCL="*"
 export SYSTEMDRIVE="C:"
+export MSBuildExtensionsPath="C:\\Program Files\\MSBuild"
+export VCTargetsPath="C:\\Program Files (x86)\\MSBuild\\Microsoft.Cpp\\v4.0\\V140"
+export PATH="/c/ninja":$PATH
+export PATH="/c/Program Files/CMake/bin":$PATH
 """
 
 def increment_pkg_config_path(source):