[ifs] Use a tmp file instead of "-"

Currently, Clang on AIX uses the system assembler to generate object files from assembly. The use of `-o -` results in a file named `-` instead of output to stdout. This patch uses a temporary object file instead.

Reviewed By: DiggerLin, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D117587