Add a broader set of compile flags.

[bryce-shang]

Issues:

Resolves CryptoAlg-626

Description of changes:

This PR added a broader set of compile flags in ./CMakeLists.txt.

Some compiler warnings are fixed in this PR:

• ISO C does not support ‘__int128’ types [-Werror=pedantic].
  • The error was in the header file of the third-party lib fiat. The warning is suppressed by __extension__.
  • Previous discussion: Fix more warnings reported by -Wpedantic. #152 (comment)
• ISO C99 doesn’t support unnamed structs/unions [-Werror=pedantic].
  • Added a name to the union.

Call-outs:

• -Wpedantic is not enabled to avoid c99 warnings.
  • One warning is CryptoAlg-626?selectedConversation=763115b6-a861-42f9-9fa5-acea8cbcb825.
  • CryptoAlg-759 is created to clarify if all code need to follow c99 spec.
• -Wno-unused-parameter is added instead of using OPENSSL_UNUSED because
  • Fixing warnings using later macro will cause more merge conflicts.
  • Some unused parameters are because not all implementations need to use all function parameters.
  • Both are just to suppress the warnings.
• -Wcast-qual is not enabled because it causes lots of false positive.
  • For example, the compiler warns const ptr is cast to ptr on macro BORINGSSL_DEFINE_STACK_OF_IMPL.
    • The compiler does not check the macro use const ptr for constptrtype.
    • The error message is linked in CryptoAlg-626?selectedConversation=5c2b0ef7-1f27-4f49-887f-7e298bf18b83
• -Wno-cast-function-type is added when the compiler is gcc8.
  • See explanation in https://gitlab.gnome.org/GNOME/gnome-terminal/-/issues/96

Testing:

How is this change tested (unit tests, fuzz tests, etc.)? Are there any testing steps to be verified by the reviewer?

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

[bryce-shang]

Make this PR as a draft. CI detects more warnings reported by the build flags due to gcc8x and aarch.