[lld] [lld] Update tests redirecting multiple commands to FileCheck (PR #156526)

[Fangrui Song via llvm-commits]

MaskRay wrote:

It's a shame that the internal shell doesn't support `(llvm-objdump --section-headers %t/test; dsymutil -s %t/test) | FileCheck %s`. The split form is more verbose and less readable. `env XXX=1` changes look good.

https://github.com/llvm/llvm-project/pull/156526