perf build: Warn about missing libelf before warning about missing libbpf

As libelf is a requirement for libbpf if it is not available, as in some
container build tests where NO_LIBELF=1 is used, then better warn about
the most basic library first.

Ditto for libz, check its availability before libbpf too.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/ZUEehyDk0FkPnvMR@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Makefile.config

@@ -680,15 +680,15 @@ ifndef BUILD_BPF_SKEL
 endif
 
 ifeq ($(BUILD_BPF_SKEL),1)
-  ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
-    dummy := $(warning Warning: Disabled BPF skeletons as libbpf is required)
-    BUILD_BPF_SKEL := 0
-  else ifeq ($(filter -DHAVE_LIBELF_SUPPORT, $(CFLAGS)),)
+  ifeq ($(filter -DHAVE_LIBELF_SUPPORT, $(CFLAGS)),)
     dummy := $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
     BUILD_BPF_SKEL := 0
   else ifeq ($(filter -DHAVE_ZLIB_SUPPORT, $(CFLAGS)),)
     dummy := $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
     BUILD_BPF_SKEL := 0
+  else ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
+    dummy := $(warning Warning: Disabled BPF skeletons as libbpf is required)
+    BUILD_BPF_SKEL := 0
   else ifeq ($(call get-executable,$(CLANG)),)
     dummy := $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
     BUILD_BPF_SKEL := 0