kbuild: Fix out-of-tree build for 'make deb-pkg'

The out-of-tree build is broken in 'make deb-pkg'. The
header checks and the header install works on the source and
not on the object tree.
While fixing this also replace the direct 'make' invocations
with the $MAKE variable to be consistent within the script.

Cc: maximilian attems <max@stro.at>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: debian-kernel@lists.debian.org
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/package/builddeb

@@ -121,7 +121,7 @@ else
 fi
 
 if grep -q '^CONFIG_MODULES=y' .config ; then
-	INSTALL_MOD_PATH="$tmpdir" make KBUILD_SRC= modules_install
+	INSTALL_MOD_PATH="$tmpdir" $MAKE KBUILD_SRC= modules_install
 	rm -f "$tmpdir/lib/modules/$version/build"
 	rm -f "$tmpdir/lib/modules/$version/source"
 	if [ "$ARCH" = "um" ] ; then
@@ -131,8 +131,8 @@ if grep -q '^CONFIG_MODULES=y' .config ; then
 fi
 
 if [ "$ARCH" != "um" ]; then
-	make headers_check
-	make headers_install INSTALL_HDR_PATH="$libc_headers_dir/usr"
+	$MAKE headers_check KBUILD_SRC=
+	$MAKE headers_install KBUILD_SRC= INSTALL_HDR_PATH="$libc_headers_dir/usr"
 fi
 
 # Install the maintainer scripts