[PATCH bpf-next v2] bpf/preload: Clean up .gitignore and "clean-files" target

[Quentin Monnet <quentin@isovalent.com>]

kernel/bpf/preload/Makefile was recently updated to have it install
libbpf's headers locally instead of pulling them from tools/lib/bpf. But
two items still need to be addressed.

First, the local .gitignore file was not adjusted to ignore the files
generated in the new kernel/bpf/preload/libbpf output directory.

Second, the "clean-files" target is now incorrect. The old artefacts
names were not removed from the target, while the new ones were added
incorrectly. This is because "clean-files" expects names relative to
$(obj), but we passed the absolute path instead. This results in the
output and header-destination directories for libbpf (and their
contents) not being removed from kernel/bpf/preload on "make clean" from
the root of the repository.

This commit fixes both issues. Note that $(userprogs) needs not be added
to "clean-files", because the cleaning infrastructure already accounts
for it.

Cleaning the files properly also prevents make from printing the
following message, for builds coming after a "make clean":
"make[4]: Nothing to be done for 'install_headers'."

v2: Simplify the "clean-files" target.

Fixes: bf60791741d4 ("bpf: preload: Install libbpf headers when building")
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
---
 kernel/bpf/preload/.gitignore | 4 +---
 kernel/bpf/preload/Makefile   | 3 +--
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/preload/.gitignore b/kernel/bpf/preload/.gitignore
index 856a4c5ad0dd..9452322902a5 100644
--- a/kernel/bpf/preload/.gitignore
+++ b/kernel/bpf/preload/.gitignore
@@ -1,4 +1,2 @@
-/FEATURE-DUMP.libbpf
-/bpf_helper_defs.h
-/feature
+/libbpf
 /bpf_preload_umd
diff --git a/kernel/bpf/preload/Makefile b/kernel/bpf/preload/Makefile
index 469d35e890eb..1400ac58178e 100644
--- a/kernel/bpf/preload/Makefile
+++ b/kernel/bpf/preload/Makefile
@@ -27,8 +27,7 @@ userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \
 
 userprogs := bpf_preload_umd
 
-clean-files := $(userprogs) bpf_helper_defs.h FEATURE-DUMP.libbpf staticobjs/ feature/
-clean-files += $(LIBBPF_OUT) $(LIBBPF_DESTDIR)
+clean-files := libbpf/
 
 $(obj)/iterators/iterators.o: | libbpf_hdrs
 
-- 
2.30.2