2025-03-26 01:40 UTC+0100 ~ Tomas Glozar [off-list ref]

The feature test for system bpftool uses BPFTOOL as the variable to set
its path, defaulting to just "bpftool" if not set by the user.

This conflicts with selftests and a few other utilities, which expect
BPFTOOL to be set to the in-tree bpftool path by default. For example,
bpftool selftests fail to build:

$ make -C tools/testing/selftests/bpf/
make: Entering directory '/home/tglozar/dev/linux/tools/testing/selftests/bpf'

make: *** No rule to make target 'bpftool', needed by '/home/tglozar/dev/linux/tools/testing/selftests/bpf/tools/include/vmlinux.h'.  Stop.
make: Leaving directory '/home/tglozar/dev/linux/tools/testing/selftests/bpf'

Fix the problem by renaming the variable used for system bpftool from
BPFTOOL to SYSTEM_BPFTOOL, so that the new usage does not conflict with
the existing one of BPFTOOL.

Reported-by: Venkat Rao Bagalkote <redacted>
Closes: https://lore.kernel.org/linux-kernel/5df6968a-2e5f-468e-b457-fc201535dd4c@linux.ibm.com/ (local)
Suggested-by: Quentin Monnet <redacted>

Let's use [off-list ref] if possible, please.

Fixes: 8a635c3856dd ("tools/build: Add bpftool-skeletons feature test")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

Looks good, thanks a lot!

Acked-by: Quentin Monnet <qmo@kernel.org>