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

[Joshua Cranmer via cfe-commits]

jcranmer-intel wrote:

> 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

But the shared library stuff isn't an issue for AMDGPU, right?

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