Relax output restrictions to make a test less flaky

Relax output restrictions to make a test less flaky

Due to random hash map traversals this test could build either crate `a` or
crate `b` first, causing the first four output lines to possibly change. Two of
the first four lines are guaranteed to be the compilation of `b` and the other
two are the compilation of `a` as well as building its build script, but no
other lines about compiling `a` can happen until the dependency `b` has finished
compiling.