The configure script checks for the existence of pthread_sigmask.
However, on FreeBSD, libc contains no-op stubs for many of the
pthread_* functions. As a result, the AC_SEARCH_LIBS macro returns
"none required".
As an alternative to checking pthread_sigmask, a solution is to check
pthread_create.
Signed-off-by: Kevin Lo <kevlo@FreeBSD.org> Acked-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Signed-off-by: Ben Pfaff <blp@nicira.com>