[PATCH v2 bpf-next] tools/bpf: add missing strings.h include

[Andrii Nakryiko <andriin@fb.com>]

Few files in libbpf are using bzero() function (defined in strings.h header), but
don't include corresponding header. When libbpf is added as a dependency to pahole,
this undeterministically causes warnings on some machines:

bpf.c:225:2: warning: implicit declaration of function ‘bzero’ [-Wimplicit-function-declaration]
  bzero(&attr, sizeof(attr));
    ^~~~~

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/bpf/bpf.c    | 1 +
 tools/lib/bpf/btf.c    | 1 +
 tools/lib/bpf/libbpf.c | 1 +
 3 files changed, 3 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 3defad77dc7a..92fd27fe0599 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -22,6 +22,7 @@
  */
 
 #include <stdlib.h>
+#include <strings.h>
 #include <memory.h>
 #include <unistd.h>
 #include <asm/unistd.h>
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index ab6528c935a1..4324eb47d214 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -4,6 +4,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 #include <errno.h>
 #include <linux/err.h>
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 47969aa0faf8..8d64ada5f728 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -18,6 +18,7 @@
 #include <libgen.h>
 #include <inttypes.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
-- 
2.17.1