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: NKirill Smelkov <kirr@nexedi.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/perf/run

@@ -30,7 +30,13 @@ unpack_git_rev () {
 }
 build_git_rev () {
 	rev=$1
-	cp ../../config.mak build/$rev/config.mak
+	for config in config.mak config.mak.autogen config.status
+	do
+		if test -e "../../$config"
+		then
+			cp "../../$config" "build/$rev/"
+		fi
+	done
 	(cd build/$rev && make $GIT_PERF_MAKE_OPTS) ||
 	die "failed to build revision '$mydir'"
 }