squid: fix ptest failure

Fix error when run ptest on target:
cp: cannot stat '/usr/bin/true': No such file or directory
make: *** [Makefile:1120: squid-conf-tests] Error 1

The correct path should be /bin/true on target.

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>

meta-networking/recipes-daemons/squid/squid_3.5.20.bb

@@ -73,6 +73,9 @@ do_install_ptest() {
     sed -e 's/^\(runtest-TESTS:\)/\1 squid-conf-tests/' \
         -e "s/\(list=' \$(TESTS)\)/\1 squid-conf-tests/" \
         -i ${D}${PTEST_PATH}/${TESTDIR}/Makefile
+
+    # Ensure the path for command true is correct
+    sed -i 's:^TRUE = .*$:TRUE = /bin/true:' ${D}${PTEST_PATH}/${TESTDIR}/Makefile
 }
 
 do_install_append() {