[lld] Update tests redirecting multiple commands to FileCheck
This patch updates two LLD tests that were redirecting multiple commands
to the same FileCheck invocation to not use this strategy. This
construction is not supported by lit's internal shell and given its
rarirty, it does not make sense to add support. The workaround is to
dump the contents of multiple commands into a file and then run
FileCheck on that.
Towards #102700.
Reviewers: petrhosek, mysterymath, cmtice, ilovepi, carlocab, MaskRay
Reviewed By: carlocab, cmtice
Pull Request: https://github.com/llvm/llvm-project/pull/156526