libcap: update LDFLAGS to find libattr.so

Signed-off-by: Kai Kang <kai.kang@windriver.com>
libcheck: fix compile error

Error message:
| In file included from timer_create.c:1:0:
| libcompat.h:133:13: error: conflicting types for 'timer_t'
|  typedef int timer_t;
|              ^
| In file included from
/buildarea/kkang/build-glibc-small-debug-aarch64/bitbake_build/tmp/sysroots/genericarmv8/usr/include/sys/type
s.h:132:0,
|                  from libcompat.h:23,
|                  from timer_create.c:1:
|
/buildarea/kkang/build-glibc-small-debug-aarch64/bitbake_build/tmp/sysroots/genericarmv8/usr/include/time.h:103:19:
note: previous
declaration of 'timer_t' was here
|  typedef __timer_t timer_t;
|                    ^

Signed-off-by: Kai Kang <kai.kang@windriver.com>