Makefile: Make sure all linker input objects exist

In case the build system builds a directory with empty Makefile,
one which does not contain any obj-y entries, the build fails to
link due to missing built-in.o .

This happens because of this part of scripts/Makefile.build
 81 ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),)
 82 builtin-target := $(obj)/built-in.o
 83 endif
which does not assign builtin-target in case obj-y is empty. The
built-in target is then not built at all, and built-in.o is not
generated by this part of scripts/Makefile.build
 325 ifdef builtin-target
 326 quiet_cmd_link_o_target = AR      $@
 327 # If the list of objects to link is empty, just create an empty built-in.o
 ...
 335 targets += $(builtin-target)
 336 endif # builtin-target
This is the correct behavior.

The final link however expects the built-in.o to exist in every directory
included in the build, even in those where the aforementioned code skipped
generation of built-in.o . Make sure the built-in.o does exist for every
directory used in final link simply by doing touch on every built-in.o used
for the link, which will create empty built-in.o in case any built-in.o is
missing.

A possible alternative fix is the always define the builtin-target
and always generate built-in.o .

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Tested-by: Quentin Schulz <quentin.schulz@cherry.de>

0 files changed, 0 insertions, 0 deletions