bv gcc by name check fix

[cyrush]

Description

Resolves #19693

Remaining cases of direct check for "gcc" were only used to set OPT compiler flags to -O2.

Removes these checks in favor of just always included -O2 as OPT where this was checked.

Type of change

• [ ] Bug fix~~
• [ ] New feature~~
• [ ] Documentation update~~
• [x] Other~~

build_visit change

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Checklist:

- [ ] I have commented my code where applicable. - [ ] I have updated the release notes. - [ ] I have made corresponding changes to the documentation. - [ ] I have added debugging support to my changes. - [ ] I have added tests that prove my fix is effective or that my feature works. - [ ] I have confirmed new and existing unit tests pass locally with my changes. - [ ] I have added new baselines for any new tests to the repo.

• [x] I have NOT made any changes to protocol or public interfaces in an RC branch.~~