[compiler-rt] [builtins] Start to refactor int to fp conversion functions to use a common implementation (PR #66903)

[Ivan Tadeu Ferreira Antunes Filho via llvm-commits]

itf wrote:

@asb  This seems to have broken some things for -target arm64-apple-ios11.0-simulator
https://github.com/llvm/llvm-project/issues/69779 

/int_to_fp_impl.inc:60:29: error: shift count is negative [-Werror,-Wshift-count-negative]
   60 |   const int dstExpBias = (1 << (dstExpBits - 1)) - 1;
      |                             ^  ~~~~~~~~~~~~~~~~
1 error generated.

https://github.com/llvm/llvm-project/pull/66903