[llvm] [clang] [flang] [mlir] [mlir][complex] Prevent underflow in complex.abs (PR #79786)

[Kai Sasaki via cfe-commits]

Lewuathe wrote:

The build which previously failed is now finished successfully.
https://lab.llvm.org/buildbot/#/builders/264/builds/6256

https://github.com/llvm/llvm-project/pull/79786