tests: add t/helper/ to the PATH with --with-dashes

We really need to be able to find the test helpers... Really. This
change was forgotten when we moved the test helpers into t/helper/

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -1227,7 +1227,7 @@ else # normal case, use ../bin-wrappers only unless $with_dashes:
 	GIT_EXEC_PATH=$GIT_BUILD_DIR
 	if test -n "$with_dashes"
 	then
-		PATH="$GIT_BUILD_DIR:$PATH"
+		PATH="$GIT_BUILD_DIR:$GIT_BUILD_DIR/t/helper:$PATH"
 	fi
 fi
 GIT_TEMPLATE_DIR="$GIT_BUILD_DIR"/templates/blt