.github: add initial github action for CI

[ericchiang]

Goal is to switch current builder run internally by Google over to
GitHub Actions.

[ericchiang]

It looks like the simulator won't build with newer versions of openssl

2021-09-01T17:34:17.7433568Z hmac.c: In function ‘TSS_rawhmac’:
2021-09-01T17:34:17.7436075Z hmac.c:384:13: error: storage size of ‘hmac’ isn’t known
2021-09-01T17:34:17.7443401Z   384 |    HMAC_CTX hmac;
2021-09-01T17:34:17.7444018Z       |             ^~~~
2021-09-01T17:34:17.7446793Z hmac.c:392:4: error: ‘HMAC_Init’ is deprecated [-Werror=deprecated-declarations]
2021-09-01T17:34:17.7447837Z   392 |    HMAC_Init(&hmac,key,keylen,EVP_sha1());
2021-09-01T17:34:17.7448477Z       |    ^~~~~~~~~
2021-09-01T17:34:17.7449752Z In file included from /usr/include/openssl/aes.h:13,
2021-09-01T17:34:17.7450468Z                  from ./tpmutil.h:45,
2021-09-01T17:34:17.7451059Z                  from hmac.c:50:
2021-09-01T17:34:17.7451790Z /usr/include/openssl/hmac.h:30:1: note: declared here
2021-09-01T17:34:17.7452633Z    30 | DEPRECATEDIN_1_1_0(__owur int HMAC_Init(HMAC_CTX *ctx, const void *key, int len,
2021-09-01T17:34:17.7453346Z       | ^~~~~~~~~~~~~~~~~~
2021-09-01T17:34:17.7497228Z hmac.c:408:4: error: implicit declaration of function ‘HMAC_cleanup’; did you mean ‘OBJ_cleanup’? [-Werror=implicit-function-declaration]
2021-09-01T17:34:17.7499707Z   408 |    HMAC_cleanup(&hmac);
2021-09-01T17:34:17.7501120Z       |    ^~~~~~~~~~~~
2021-09-01T17:34:17.7501641Z       |    OBJ_cleanup
2021-09-01T17:34:17.7509658Z hmac.c:408:4: error: nested extern declaration of ‘HMAC_cleanup’ [-Werror=nested-externs]
2021-09-01T17:34:17.7513005Z hmac.c:384:13: error: unused variable ‘hmac’ [-Werror=unused-variable]
2021-09-01T17:34:17.7513876Z   384 |    HMAC_CTX hmac;
2021-09-01T17:34:17.7514371Z       |             ^~~~
2021-09-01T17:34:17.7542668Z cc1: all warnings being treated as errors

Talked to @twitchy-jsonp and I think it might be time to retire TPM 1.2 support...

[ericchiang]

Another note. The tests currently don't build on MacOS or Windows, even with openssl installed. Opened #240