Skip /clr tests

[Stephan T. Lavavej (StephanTLavavej)]

Fixes #788. We don't yet build /clr support libraries, so we shouldn't attempt to test them. (This fails on my machine, for some reason; on other machines it tests a Frankenstein combination of STL OSS and released VS code.)

Additionally, this changes the Python logic to use exact matches for compiler options instead of startswith. This doesn't make a difference given the current ordering (looking for clr:pure first) and our current compiler options, but I believe this is more robust (given the existence of /clr:meow variants). As before, we ignore the first character because MSVC supports -meow and /meow option styles.

This PR resolves an enormous number of test failures on my machine. Now, the test log looks like:

    {
      "code": "UNSUPPORTED",
      "elapsed": 0.0009999275207519531,
      "name": "std :: tests/Dev08_496675_iostream_int_reading:19",
      "output": "Test requires the following unavailable features: clr"
    },
    {
      "code": "UNSUPPORTED",
      "elapsed": 0.0,
      "name": "std :: tests/Dev08_496675_iostream_int_reading:20",
      "output": "Test requires the following unavailable features: clr"
    },
    {
      "code": "UNSUPPORTED",
      "elapsed": 0.0,
      "name": "std :: tests/Dev08_496675_iostream_int_reading:21",
      "output": "Test requires the following unavailable features: clr_pure"
    },
    {
      "code": "UNSUPPORTED",
      "elapsed": 0.0,
      "name": "std :: tests/Dev08_496675_iostream_int_reading:22",
      "output": "Test requires the following unavailable features: clr_pure"
    },
    {
      "code": "UNSUPPORTED",
      "elapsed": 0.0,
      "name": "std :: tests/Dev08_496675_iostream_int_reading:23",
      "output": "Test requires the following unavailable features: edg"
    },
    {
      "code": "UNSUPPORTED",
      "elapsed": 0.0009996891021728516,
      "name": "std :: tests/Dev08_496675_iostream_int_reading:24",
      "output": "Test requires the following unavailable features: edg"
    },
    {
      "code": "UNSUPPORTED",
      "elapsed": 0.0,
      "name": "std :: tests/Dev08_496675_iostream_int_reading:25",
      "output": "Test requires the following unavailable features: edg"
    },

I verified that the configuration numbers for /clr, /clr:pure, and /BE correspond to the lines in the test matrix.

I believe this is my first 100% Python PR. 😸

[Curtis J Bezault (cbezault)]

UNSUPPORTED isn't a test failure. It just means the prerequisites to run the test are not satisfied.

[Stephan T. Lavavej (StephanTLavavej)]

UNSUPPORTED isn't a test failure. It just means the prerequisites to run the test are not satisfied.

Yep, I understand. Before this change, /clr outright failed for me, due to missing mscoree.lib. Now it's unsupported, which is good.

[Curtis J Bezault (cbezault)]

Oh woops, I misread the description as complaining that you were getting UNRESOLVEDs as opposed to describing the behavior you were now seeing.