bpftool: Remove redundant slashes

Because the OUTPUT variable ends with a slash but CURDIR doesn't, to keep
the _OUTPUT value consistent, we add a trailing slash to CURDIR when
defining _OUTPUT variable.

Since the _OUTPUT variable holds a value ending with a trailing slash,
there is no need to add another one when defining BOOTSTRAP_OUTPUT and
LIBBPF_OUTPUT variables. Likewise, when defining LIBBPF_INCLUDE and
LIBBPF_BOOTSTRAP_INCLUDE, we shouldn't add an extra slash either for the
same reason.

When building libbpf, the value of the DESTDIR argument should also not
end with a trailing slash.

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220226163815.520133-1-ytcoode@gmail.com

tools/bpf/bpftool/Makefile

@@ -18,19 +18,19 @@ BPF_DIR = $(srctree)/tools/lib/bpf
 ifneq ($(OUTPUT),)
   _OUTPUT := $(OUTPUT)
 else
-  _OUTPUT := $(CURDIR)
+  _OUTPUT := $(CURDIR)/
 endif
-BOOTSTRAP_OUTPUT := $(_OUTPUT)/bootstrap/
+BOOTSTRAP_OUTPUT := $(_OUTPUT)bootstrap/
 
-LIBBPF_OUTPUT := $(_OUTPUT)/libbpf/
+LIBBPF_OUTPUT := $(_OUTPUT)libbpf/
 LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)
-LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include
+LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)include
 LIBBPF_HDRS_DIR := $(LIBBPF_INCLUDE)/bpf
 LIBBPF := $(LIBBPF_OUTPUT)libbpf.a
 
 LIBBPF_BOOTSTRAP_OUTPUT := $(BOOTSTRAP_OUTPUT)libbpf/
 LIBBPF_BOOTSTRAP_DESTDIR := $(LIBBPF_BOOTSTRAP_OUTPUT)
-LIBBPF_BOOTSTRAP_INCLUDE := $(LIBBPF_BOOTSTRAP_DESTDIR)/include
+LIBBPF_BOOTSTRAP_INCLUDE := $(LIBBPF_BOOTSTRAP_DESTDIR)include
 LIBBPF_BOOTSTRAP_HDRS_DIR := $(LIBBPF_BOOTSTRAP_INCLUDE)/bpf
 LIBBPF_BOOTSTRAP := $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
 
@@ -44,15 +44,15 @@ $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DI
 
 $(LIBBPF): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_OUTPUT)
 	$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) \
-		DESTDIR=$(LIBBPF_DESTDIR) prefix= $(LIBBPF) install_headers
+		DESTDIR=$(LIBBPF_DESTDIR:/=) prefix= $(LIBBPF) install_headers
 
 $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_DIR)
 	$(call QUIET_INSTALL, $@)
 	$(Q)install -m 644 -t $(LIBBPF_HDRS_DIR) $<
 
 $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
 	$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
-		DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR) prefix= \
+		DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR:/=) prefix= \
 		ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
 
 $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR)