I fixed a similar build error in commit 1b1e4ee86e ("sh: fix build
error for empty CONFIG_BUILTIN_DTB_SOURCE"), but it came back again.
Since commit 37c8a5fafa ("kbuild: consolidate Devicetree dtb
build rules"), the combination of CONFIG_OF_EARLY_FLATTREE=y and
CONFIG_USE_BUILTIN_DTB=n results in the following build error:
make[1]: *** No rule to make target 'arch/sh/boot/dts/.dtb.o',
needed by 'arch/sh/boot/dts/built-in.a'. Stop.
Prior to that commit, there was only one path to descend into
arch/sh/boot/dts/, and arch/sh/Makefile correctly guards it with
CONFIG_USE_BUILTIN_DTB:
core-$(CONFIG_USE_BUILTIN_DTB) += arch/sh/boot/dts/
Now, there is another path to descend there from the top Makefile
when CONFIG_OF_EARLY_FLATTREE=y. If CONFIG_USE_BUILTIN_DTB is disabled,
CONFIG_BUILTIN_DTB_SOURCE is invisible instead of defined as "".
Add obj-$(CONFIG_USE_BUILTIN_DTB) guard to avoid the attempt to build
the non-existing file.
Fixes: 37c8a5fafa ("kbuild: consolidate Devicetree dtb build rules")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
207a369e3c