[crosperf] Fix xbuddy to work with new -toolchain builders.

The xbuddy translating code was improperly prepending to board
name to the waterfall builder trybot images (the ones with the
generic architecture names).  This CL fixes that.

BUG=chromium:653210
TEST=Tested crosperf with 'build: x86-llvm-toolchain/R55-8865.0.0-rc1';
failed without this CL, worked with it.

Change-Id: I706c9d882f9c99f8af11eb1782ea6edd1eedbfe5
Reviewed-on: https://chrome-internal-review.googlesource.com/293815
Commit-Ready: Caroline Tice <cmtice@google.com>
Tested-by: Caroline Tice <cmtice@google.com>
Reviewed-by: Yunlian Jiang <yunlian@google.com>
1 file changed