tools lib: Guard the strlcpy() header with __GLIBC__

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 <[email protected]>
Cc: Alexey Brodkin <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>