t3008: find test-tool through path lookup

Do not use $GIT_BUILD_DIR without quotes; it may contain spaces and be
split into fields. But it is not necessary to access test-tool with an
absolute path in the first place as it can be found via path lookup.
Remove the explicit path.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3008-ls-files-lazy-init-name-hash.sh

diff --git a/t/t3008-ls-files-lazy-init-name-hash.sh b/t/t3008-ls-files-lazy-init-name-hash.sh
index 64f0473..85f3704 100755
--- a/t/t3008-ls-files-lazy-init-name-hash.sh
+++ b/t/t3008-ls-files-lazy-init-name-hash.sh
@@ -4,7 +4,7 @@
 
 . ./test-lib.sh
 
-if test 1 -eq $($GIT_BUILD_DIR/t/helper/test-tool online-cpus)
+if test 1 -eq $(test-tool online-cpus)
 then
 	skip_all='skipping lazy-init tests, single cpu'
 	test_done