retrace: better error reporting For a resonable error reporting the output must be captured. Print the output on error only, if it is not written anyway. Bug: angleproject:7800 Change-Id: Ie0ca819b7e269317073f8f1c79819e35a33a4325 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4003220 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Gert Wollny <gert.wollny@collabora.com>