Disable fuzztest subprocess library on Apple tvOS

[abhijeetk]

On tvOS, creating child processes is forbidden at an API level, so the
posix_spawn_* functions used by FuzzTest in the subprocess code cause
build errors.

This change disables the subprocess library on Apple tvOS to avoid
calling unsupported functions.

This isssue is similar to b222049

Co-Authored-By: [email protected]

[rakuco]

In our Chromium fork for Apple tvOS, we build against the tvOS SDK.

I think this PR makes sense even without mentioning Chromium, as these changes help anyone trying to build and use fuzz tests on tvOS.

[rakuco]

I'd still reword the first paragraph of the PR message. Saying that tvOS builds use the tvOS SDK is redundant, so something like this should suffice:

In our Apple tvOS build environment, we compile FuzzTest against the
tvOS SDK.

On tvOS, creating child processes is forbidden at an API level, so the posix_spawn_* functions used by FuzzTest in the subprocess code cause build errors.

[rakuco]

Looks fine to me!

@lszekeres could you take a look at this PR? The CMake codelab check seems to be failing because the code assumes that the PR branch was pushed to the google/fuzztest repository rather than a fork.

[abhijeetk]

@lszekeres Is this failure caused by an issue in the internal tooling or framework?
Can I help with testing or fixing it?

Also, is it related to this(07d3d31) patch that's supposed to fix the CMake build failure

Thanks!

[rakuco]

@abhijeetk you can try amending the commit to change the hash and force-pushing your branch to trigger the CI again, that commit should've fixed things.

[abhijeetk]

Hi @lszekeres, I think we’re very close. The GCC build appears to be failing, but I couldn’t find a specific error message in the logs. Do you have any insight into what might be causing it?

[abhijeetk]

Thanks everyone for review.

[lszekeres]

Thanks for the PR!