[clang] Disable FTZ/DAZ when compiling shared libraries by default. (PR #80475)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> So overall, the practical effect of the `denormal-fp-math` attribute being set incorrectly doesn't appear to matter.

It matters more for AMDGPU, where we need to care because some instructions just don't respect denormals. We legalize some operations differently depending on the mode 


https://github.com/llvm/llvm-project/pull/80475