insane.bbclass: make the checking stricter for unsafe references in scripts

Previously, the checking for unsafe references is not strict enough. It
only checks whether '/usr/' is in the script. As a result, any script
containing statements like below will match this check.

	   PATH="/bin:/sbin:/usr/bin:/usr/sbin"

However, as we can see, this is actually not an unsafe reference. What
we really want to check is something like '/usr/bin/tail', so we should
make the checking stricter.

This patch solves the QA warning in gzip and nfs-utils.

(From OE-Core rev: f818f7359c1a5db2c5c041c42eecb9f0434d9800)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/insane.bbclass

@@ -428,7 +428,7 @@ def package_qa_check_unsafe_references_in_scripts(path, name, d, elf, messages):
         if bool(statinfo.st_mode & stat.S_IXUSR):
             # grep shell scripts for possible references to /exec_prefix/
             exec_prefix = d.getVar('exec_prefix', True)
-            statement = "grep -e '%s/' %s > /dev/null" % (exec_prefix, path)
+            statement = "grep -e '%s/[^ :]\{1,\}/[^ :]\{1,\}' %s > /dev/null" % (exec_prefix, path)
             if subprocess.call(statement, shell=True) == 0:
                 error_msg = pn + ": Found a reference to %s/ in %s" % (exec_prefix, path)
                 package_qa_handle_error("unsafe-references-in-scripts", error_msg, d)