libbpf: Disable -Wswitch-enum compiler warning

That compilation warning is more annoying, than helpful.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200818213356.2629020-2-andriin@fb.com

tools/lib/bpf/Makefile

@@ -107,7 +107,7 @@ ifeq ($(feature-reallocarray), 0)
 endif
 
 # Append required CFLAGS
-override CFLAGS += $(EXTRA_WARNINGS)
+override CFLAGS += $(EXTRA_WARNINGS) -Wno-switch-enum
 override CFLAGS += -Werror -Wall
 override CFLAGS += -fPIC
 override CFLAGS += $(INCLUDES)