tools lib: Guard the strlcpy() header with __GLIBC__

Better to whitelist it for libraries that require it (glibc) than
blacklist it with the ones that don't (uclibc, musl libc, etc).

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-52ih0m63a2n63tanpy6yj682@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/include/linux/string.h

@@ -8,7 +8,7 @@ void *memdup(const void *src, size_t len);
 
 int strtobool(const char *s, bool *res);
 
-#ifndef __UCLIBC__
+#ifdef __GLIBC__
 extern size_t strlcpy(char *dest, const char *src, size_t size);
 #endif