[llvm] [flang-rt][build] Disable build-time warning of '-Wshift-count-negative' from g++ compiler and remove unsupported floating-point data. (PR #174915)

[Eugene Epshteyn via llvm-commits]

eugeneepshteyn wrote:

Note: if you have several PRs to test, it may be possible to run llvm-test-suite on both of them, to save you time.

https://github.com/llvm/llvm-project/pull/174915