bpf: Replace deprecated -target with --target= for Clang

The -target option has been deprecated since clang 3.4 in 2013. Therefore, use
the preferred --target=bpf form instead. This also matches how we use --target=
in scripts/Makefile.clang.

Signed-off-by: Fangrui Song <maskray@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: 274b6f0c87
Link: https://lore.kernel.org/bpf/20230624001856.1903733-1-maskray@google.com

tools/bpf/bpftool/Documentation/bpftool-gen.rst

@@ -260,9 +260,9 @@ EXAMPLES
 This is example BPF application with two BPF programs and a mix of BPF maps
 and global variables. Source code is split across two source code files.
 
-**$ clang -target bpf -g example1.bpf.c -o example1.bpf.o**
+**$ clang --target=bpf -g example1.bpf.c -o example1.bpf.o**
 
-**$ clang -target bpf -g example2.bpf.c -o example2.bpf.o**
+**$ clang --target=bpf -g example2.bpf.c -o example2.bpf.o**
 
 **$ bpftool gen object example.bpf.o example1.bpf.o example2.bpf.o**
 

tools/bpf/bpftool/Makefile

@@ -216,7 +216,7 @@ $(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF_BOOTSTRAP)
 		-I$(srctree)/tools/include/uapi/ \
 		-I$(LIBBPF_BOOTSTRAP_INCLUDE) \
 		-g -O2 -Wall -fno-stack-protector \
-		-target bpf -c $< -o $@
+		--target=bpf -c $< -o $@
 	$(Q)$(LLVM_STRIP) -g $@
 
 $(OUTPUT)%.skel.h: $(OUTPUT)%.bpf.o $(BPFTOOL_BOOTSTRAP)

tools/bpf/runqslower/Makefile

@@ -62,7 +62,7 @@ $(OUTPUT)/%.skel.h: $(OUTPUT)/%.bpf.o | $(BPFTOOL)
 	$(QUIET_GEN)$(BPFTOOL) gen skeleton $< > $@
 
 $(OUTPUT)/%.bpf.o: %.bpf.c $(BPFOBJ) | $(OUTPUT)
-	$(QUIET_GEN)$(CLANG) -g -O2 -target bpf $(INCLUDES)		      \
+	$(QUIET_GEN)$(CLANG) -g -O2 --target=bpf $(INCLUDES)		      \
 		 -c $(filter %.c,$^) -o $@ &&				      \
 	$(LLVM_STRIP) -g $@