The symbol determines if the libevent2-pthreads libraries get built or not.
If we want to select libevent2-pthreads, and these haven't been built, an
error will occur mentioning that there are no 'libevent_pthreads-2.1.so'
files.
Adding CONFIG_PACKAGE_libevent2-pthreads to PKG_CONFIG_DEPEND will make
sure that the libraries get re-built in case libevent2-pthreads is
selected.
Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
