Fix presubmit for hidden api.

grep returns 1 for if nothing was found. This fails presubmit hook due
to bash handling "set -e" Looks like grep not found is valid case.
This fixes this issue by bypassing grep exit code.

Test: Locally
Bug: 161351699
Merged-In: I39e926a348a0fb8f4040f86034affdb4204faac5
Change-Id: I39e926a348a0fb8f4040f86034affdb4204faac5
(cherry picked from commit e6a5253f12)

tools/hiddenapi/exclude.sh

@@ -35,7 +35,7 @@ TEAMS=LIBCORE
 PACKAGES=$(for t in $TEAMS; do echo $(eval echo \${${t}_PACKAGES}); done)
 RE=$(echo ${PACKAGES} | sed "s/ /|/g")
 git show --name-only --pretty=format: $1 | grep "config/hiddenapi-.*txt" | while read file; do
-    ENTRIES=$(grep -E "^L(${RE})/" <(git show $1:$file))
+    ENTRIES=$(grep -E "^L(${RE})/" || true <(git show $1:$file))
     if [[ -n "${ENTRIES}" ]]; then
       echo -e "\e[1m\e[31m$file $1 contains the following entries\e[0m"
       echo -e "\e[1m\e[31mfor packages that are handled using UnsupportedAppUsage. Please remove\e[0m"