[clang] [Driver] Introduce ffp-model=aggressive (PR #100453)

[Joshua Cranmer via cfe-commits]

================
@@ -1766,7 +1768,10 @@ for more details.
      ``STDC FENV_ACCESS``: by default ``FENV_ACCESS`` is disabled. This option
      setting behaves as though ``#pragma STDC FENV_ACCESS ON`` appeared at the
      top of the source file.
-   * ``fast`` Behaves identically to specifying both ``-ffast-math`` and
+   * ``fast`` Behaves identically to specifying ``-funsafe-math-optimizations``,
+     ``-fno-math-errno`` and ``-fcomplex-arithmetic=promoted``
+     ``ffp-contract=fast``
----------------
jcranmer-intel wrote:

fast-honor-pragmas, no?

https://github.com/llvm/llvm-project/pull/100453