futility: stop using the symlink names in utility scripts

We still create the symlinks (FOO -> futility), but this
change invokes those built-in functions with "futility FOO ..."
instead of using the FOO symlink.

Note that the scripts/ directory is unchanged. That's a
separate CL, since we don't have tests for that.

BUG=chromium:231547
BRANCH=ToT
TEST=make runtests

In addition to running "make runtests", I temporarily
modified the Makefile to avoid creating the symlinks at all.
The tests still passed.

Change-Id: I96863259b9df02a3611f759a7509bf4090ae03e8
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/216717
Reviewed-by: Randall Spangler <rspangler@chromium.org>
diff --git a/tests/gen_test_keys.sh b/tests/gen_test_keys.sh
index 5575cd5..79fabf1 100755
--- a/tests/gen_test_keys.sh
+++ b/tests/gen_test_keys.sh
@@ -38,14 +38,14 @@
     do
       alg=$((${key_index} * 3 + ${alg_index}))
   # wrap the public key
-      ${BIN_DIR}/vbutil_key \
+      ${FUTILITY} vbutil_key \
         --pack "${key_base}.sha${sha_type}.vbpubk" \
         --key "${key_base}.keyb" \
         --version 1 \
         --algorithm ${alg}
 
   # wrap the private key
-      ${BIN_DIR}/vbutil_key \
+      ${FUTILITY} vbutil_key \
         --pack "${key_base}.sha${sha_type}.vbprivk" \
         --key "${key_base}.pem" \
         --algorithm ${alg}