Fix bad logic that prevented -fp-model=precise from being used.

[KineticTheory]

Purpose of Pull Request

• Fixes re-git issue #41

Status

• Reference:
  • Pre-Merge Code Review
  • CDash Status
• Checks
  • [ ] Travis/Appveyor CI checks pass
  • [ ] Code coverage does not decrease
  • [ ] Valgrind test passes
  • [ ] Toss3 checks pass
  • [ ] Trinitite checks pass
  • [ ] Code reviewed/approved, sufficient DbC checks, testing, documentation

[attom]

@jhchang-lanl do we need this change too?

[jhchang-lanl]

@attom No.