bpftool: Link zstd lib required by libelf

When the feature libelf-zstd is detected, the zstd lib is required by
libelf.  Link the zstd lib in this case.

Reviewed-by: Quentin Monnet <[email protected]>
Signed-off-by: Leo Yan <[email protected]>
Tested-by: Namhyung Kim <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: Eduard Zingerman <[email protected]>
Cc: Guilherme Amadio <[email protected]>
Cc: Hao Luo <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Fastabend <[email protected]>
Cc: KP Singh <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Cc: Nick Terrell <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Stanislav Fomichev <[email protected]>
Cc: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: Leo-Yan

src/Makefile

@@ -104,6 +104,7 @@ FEATURE_TESTS += libbfd-liberty
 FEATURE_TESTS += libbfd-liberty-z
 FEATURE_TESTS += disassembler-four-args
 FEATURE_TESTS += disassembler-init-styled
+FEATURE_TESTS += libelf-zstd
 
 FEATURE_DISPLAY := clang-bpf-co-re
 FEATURE_DISPLAY += llvm
@@ -126,6 +127,12 @@ endif
 
 LIBS = $(LIBBPF) -lelf -lz
 LIBS_BOOTSTRAP = $(LIBBPF_BOOTSTRAP) -lelf -lz
+
+ifeq ($(feature-libelf-zstd),1)
+LIBS += -lzstd
+LIBS_BOOTSTRAP += -lzstd
+endif
+
 ifeq ($(feature-libcap), 1)
 CFLAGS += -DUSE_LIBCAP
 LIBS += -lcap