Support LLVM Flang (flang-new)

[rouson]

This PR

1. Fixes a code conformance issues that flang identified.
2. Switches a sync all statement to call prif_sync_all()
3. Updates install.sh to add flags required for assumed-rank support if llvm is detected in $FPM_CC --version.

fpm test fails due to a code conformance problem in Veggies. An issue will be submitted on the Veggies repository.

[everythingfunctional]

I think the tests that are failing are due to the line result_ = assert_that(all(scramlet == co_max_scramlet),"all(scramlet == co_max_scramlet)"), which should use expected_scramlet instead. It may be worth adding 1, 2 and 3d arrays of strings for assert_equals to veggies, as showing the actual arrays in the failure message would make this easier to diagnose.

[bonachea]

@rouson do you want to cherry-pick the commits from PR #142 into this one, or does it make sense to keep them as separate pull requests?

[rouson]

@rouson do you want to cherry-pick the commits from PR #142 into this one, or does it make sense to keep them as separate pull requests?

@bonachea I just tagged you in a comment on PR #142 and merged that one. @ktras is taking over development on this branch.

@ktras you might want to merge main into this branch or rebase this branch off of main, which would likely go through cleanly because the new commit that I just merged into main is orthogonal to the commits on this branch as far a I recall.

[ktras]

@rouson I think will rebase this branch with main once PR #143 is merged in main. Because we need those changes on this branch as well.