Revert "The _Float16 type is supported on x86 systems with SSE2 enabled."

This reverts commit 6623c02d70c3732dbea59c6d79c69501baf9627b.
The change seems to be breaking build of compiler-rt on Debian.

GitOrigin-RevId: fd759d42c9f84d16efa99a59620cbb3e6836fed4
9 files changed