depmod: handle the case of /sbin/depmod without /sbin in PATH

Commit 436e980e ("kbuild: don't hardcode depmod path") stopped
hard-coding the path of depmod, but in the process caused trouble for
distributions that had that /sbin location, but didn't have it in the
PATH (generally because /sbin is limited to the super-user path).

Work around it for now by just adding /sbin to the end of PATH in the
depmod.sh script.
Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/depmod.sh

@@ -15,6 +15,8 @@ if ! test -r System.map ; then
 	exit 0
 fi
 
+# legacy behavior: "depmod" in /sbin, no /sbin in PATH
+PATH="$PATH:/sbin"
 if [ -z $(command -v $DEPMOD) ]; then
 	echo "Warning: 'make modules_install' requires $DEPMOD. Please install it." >&2
 	echo "This is probably in the kmod package." >&2