[CrashReproducer] Handle indexing turned on with CLANG_PROJECT_INDEX_PATH.

[vsapsai]

Crash reproducer is checking the driver's arguments for
-index-store-path and in case of the environment variable, this
argument is absent. So the generated reproducer incorrectly won't run
the indexer.

Fix by checking the arguments of the failed -cc1 command for
-index-store-path.

rdar://problem/48830606

[jkorous-apple]

@swift-ci please test

[jkorous-apple]

@vsapsai just wondering - how do we handle other environment variables in reproducers? Strictly speaking this isn't a 100% accurate reproducer (although for all practical purposes it shouldn't matter).

[vsapsai]

@vsapsai just wondering - how do we handle other environment variables in reproducers? Strictly speaking this isn't a 100% accurate reproducer (although for all practical purposes it shouldn't matter).

Good question. Need to double check but my impression is that the reproducer contains -cc1 options and environment variables are handled by the driver. So all the extra stuff the driver has added should be preserved. But -index-store-path is special because we don't preserve its value verbatim but change to a different one in the reproducer directory. That's how it slipped through the cracks.