hadrian: Don't capture RunTest output
There are a few reasons why capturing the output of the RunTest builder is undesirable:
-
there is a large amount of output which then gets unnecessarily duplicated by Hadrian if the builder fails
-
the output may contain codepoints which are unrepresentable in the current codepage on Windows, causing Hadrian to crash
-
capturing the output causes the testsuite driver to disable its colorisation logic, making the output less legible.