kbuild: make missing $DEPMOD a Warning instead of an Error

When $DEPMOD is not found, only print a warning instead of exiting
with an error message and error status:

Warning: 'make modules_install' requires /sbin/depmod. Please install it.
This is probably in the kmod package.

Change the Error to a Warning because "not all build hosts for cross
compiling Linux are Linux systems and are able to provide a working
port of depmod, especially at the file patch /sbin/depmod."

I.e., "make modules_install" may be used to copy/install the
loadable modules files to a target directory on a build system and
then transferred to an embedded device where /sbin/depmod is run
instead of it being run on the build system.

Fixes: 934193a ("kbuild: verify that $DEPMOD is installed")
Signed-off-by: Randy Dunlap <[email protected]>
Reported-by: H. Nikolaus Schaller <[email protected]>
Cc: [email protected]
Cc: Lucas De Marchi <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Chih-Wei Huang <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

Author: rddunlap

scripts/depmod.sh

@@ -15,9 +15,9 @@ if ! test -r System.map ; then
 fi
 
 if [ -z $(command -v $DEPMOD) ]; then
-	echo "'make modules_install' requires $DEPMOD. Please install it." >&2
+	echo "Warning: 'make modules_install' requires $DEPMOD. Please install it." >&2
 	echo "This is probably in the kmod package." >&2
-	exit 1
+	exit 0
 fi
 
 # older versions of depmod require the version string to start with three