Warning that Apple support is disabled

[monkeynova]

I went to try out this library and got it linked and compiling, but couldn't figure out why my tests weren't registered or running. It took me a while of digging before I found the following.

It would have been really nice to have gotten a warning during compilation, rather than silently dropping the test, to know that what I was trying wasn't supported.

// Temporarily disable fuzz tests under MSVC/iOS/MacOS.
// They might not support all the C++17 features we are using right now.
// Disables all registration and disables running the domain expressions by
// using a ternary expression. The tail code (eg .WithDomains(...)) will not be
// executed.
#if defined(__APPLE__) || defined(_MSC_VER)
#undef FUZZ_TEST
...

[hareen-kancharla]

Thank you! This saved me some time, while I was trying to understand why the sample test was failing when built on MacOS. In my case I was seeing the following error.

[.] Sanitizer coverage enabled. Counter map size: 66654, Cmp map size: 262144
Note: Google Test filter = MyTestSuite.IntegerAdditionCommutes
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from MyTestSuite
[ RUN      ] MyTestSuite.IntegerAdditionCommutes
FUZZTEST_PRNG_SEED=uBLMuOP9NJMZB3eYHAFWsVe3m1wWzCrlibqlIFasoeg
Internal error! Check (!corpus_.empty()) failed: No seed input coverage registered. Test function might be uninstrumented?
[1]    71485 abort      MallocNanoZone=0 ./first_fuzz_test --fuzz=MyTestSuite.IntegerAdditionCommutes

[YungRaj]

Working as of ae6208f. See https://github.com/YungRaj/DarwinKit to observe the dependencies used, WORKSPACE, .blazerc, etc files