fix: t_local_cache_threading.c:85:12: error: incompatible pointer to integer conversion

[dawesc]

Unable to compile on Mac without a static cast to ensure the return type of the thread id.

Issue #807

Description of changes:
Static cast the thread pointer returned so that on MacOs it compiles

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Check any applicable:

• Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.

[texastony]

Copying some testing logs from the CodeBuild execution on Identifier: build_test_static_debug:

43/43 Test #4: static_test_vectors ........................***Failed 204.50 sec

Decryption successfully completed for 8208 test cases and failed for 1.
AES Passed = 4901, RSA Passed = 1320, KMS Passed = 1320, Encrypt-only = 0, Not-yet-supported = 880.

98% tests passed, 1 tests failed out of 43
Total Test time (real) = 204.55 sec
The following tests FAILED:
      4 - static_test_vectors (Failed)

I do not have time to dig into these right now,
but it appears that only one static test vector failed.

I kicked off a retry, on the chance that it was a transient failure.

The GitHub MacOS builds also failed.

The retry succeeded! But the Webhook is not going to pole CodeBuild again.
Which means only the macOS builds and test-clang-format need to be addressed.

[dawesc]

Hi there, many thanks for your efforts; I've fixed the linting. Am I ok to leave the macOS install issue with you as it looks to be a problem with test environments? file cannot create directory: /usr/local/lib/cmake/AWSSDK. Maybe need administrative privileges.

[texastony]

I ran the MacOS CI on HEAD and got the same results;
it clearly is nothing related to this PR.
#809