Basic: adjust the reported subprocess id
Basic: adjust the reported subprocess id

Adjust the reported error to use the first string in the command line.
This is needed to ensure that we use the correct value on Windows.  THis
allows the Windows build to get further.

apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild