[half] Update to version 1.12.0

Update repository to contain version 1.12.0. Files taken from
https://sourceforge.net/projects/half/files/half/1.12.0/half-1.12.0.zip/download.

Bug: 230037502
Change-Id: I8a3feedd59c15d1a91ca104f9bc46fad7811de89
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/half/+/1256065
Reviewed-by: Hunter Freyer <hjfreyer@google.com>