t/perf/run: copy config.mak.autogen & friends to build area
Otherwise for people who use autotools-based configure in main worktree,
the performance testing results will be inconsistent as work and build
trees could be using e.g. different optimization levels.
See e.g.
http://public-inbox.org/git/
20160818175222.bmm3ivjheokf2qzl@sigill.intra.peff.net/
for example.
NOTE config.status has to be copied because otherwise without it the build
would want to run reconfigure this way loosing just copied config.mak.autogen.
Signed-off-by: Kirill Smelkov <kirr@nexedi.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>