[PATCH] kbuild: cancel sub_make_done for the install target to fix DKMS

[Masahiro Yamada]

Since commit bcf637f54f6d ("kbuild: parse C= and M= before changing the
working directory"), external modules invoked by DKMS fail to build
because M= option is not parsed.

I wanted to add 'unset sub_make_done' in install.sh but similar scripts,
arch/*/boot/install.sh, are duplicated, so I set sub_make_done empty
in the top Makefile.

Fixes: bcf637f54f6d ("kbuild: parse C= and M= before changing the working directory")
Reported-by: John S Gruber <johnsgruber@xxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

 Makefile | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Makefile b/Makefile
index bb10a93edf5c..4193092f7c38 100644
--- a/Makefile
+++ b/Makefile
@@ -1316,6 +1316,16 @@ PHONY += scripts_unifdef
 scripts_unifdef: scripts_basic
 	$(Q)$(MAKE) $(build)=scripts scripts/unifdef
 
+# ---------------------------------------------------------------------------
+# Install
+
+# Many distros have the custom install script, /sbin/kernelinstall.
+# If DKMS is installed, 'make install' will eventually recuses back
+# to the this Makefile to build and install external modules.
+# Cancel sub_make_done so that options such as M=, V=, etc. are parsed.
+
+install: sub_make_done=
+
 # ---------------------------------------------------------------------------
 # Tools
 
-- 
2.27.0