build: support eBPF programs in nested directories

The current build system sets the name of the generated
skeleton directly to the file's name minus the .skel.h suffix.
Passing names of eBPF targets that contain a directory will
result in wrong program names and syntax errors in the skeleton
source file. The commit pops out the directory part from the name.
This change doesn't affect the current programs in the repository
but adds the feature to have to have eBPF code in special directories.

Signed-off-by: Jalal Mostafa <[email protected]>

lib/common.mk

@@ -66,7 +66,7 @@ all: $(USER_TARGETS) $(XDP_OBJ) $(EXTRA_TARGETS) $(TEST_TARGETS) man
 
 .PHONY: clean
 clean::
-	$(Q)rm -f $(USER_TARGETS) $(XDP_OBJ) $(TEST_TARGETS) $(USER_OBJ) $(TEST_OBJ) $(USER_GEN) $(BPF_SKEL_H) *.ll
+	$(Q)rm -f $(USER_TARGETS) $(XDP_OBJ) $(TEST_TARGETS) $(USER_OBJ) $(TEST_OBJ) $(USER_GEN) $(BPF_SKEL_H) *.ll **/*.ll
 
 .PHONY: install
 install: all install_local
@@ -121,7 +121,7 @@ $(XDP_OBJ): %.o: %.c $(KERN_USER_H) $(EXTRA_DEPS) $(BPF_HEADERS) $(LIBMK)
 	$(QUIET_LLC)$(LLC) -march=$(BPF_TARGET) -filetype=obj -o $@ ${@:.o=.ll}
 
 $(BPF_SKEL_H): %.skel.h: %.bpf.o
-	$(QUIET_GEN)$(BPFTOOL) gen skeleton $< name ${@:.skel.h=} > $@
+	$(QUIET_GEN)$(BPFTOOL) gen skeleton $< name $(notdir ${@:.skel.h=}) > $@
 
 .PHONY: man
 ifeq ($(EMACS),)