Previously, each job would overwrite the -MJ file. This didn't quite work for Clang invocations with multiple architectures, which got fixed in D121997 by always appending to the -MJ file. That's not correct either, since the file would grow indefinitely on subsequent Clang invocations. This patch ensures the driver always removes the file before jobs fill it in by appending.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D128098
Command lines with multiple `-arch` arguments expand into multiple entries in the compilation database. However, the file writes are not appending, meaning subsequent writes end up overwriting the previous ones, resulting in garbled output.
This patch fixes that by always appending to the file.
rdar://90165004
Reviewed By: dexonsmith
Differential Revision: https://reviews.llvm.org/D121997
