build fails on solairs: no suitable polling system found

While the build system works fine in version 3.2.x, version 4.0.3 complains that no suitable polling system was found:

[...]
checking whether to install manpages... yes
checking for suitable polling system... no suitable polling system found
configure: error: Unable to continue without polling system

The only difference I found is that the checks have been moved from configure.in to configure.ac.

3.2.x:

zeromq-3.2.4/configure.in:# Check polling system
zeromq-3.2.4/configure.in:LIBZMQ_CHECK_POLLER([CPPFLAGS="${CPPFLAGS} -D${libzmq_cv_poller_flag}"],
zeromq-3.2.4/configure.in: [AC_MSG_ERROR([Unable to continue without polling system])])

4.0.3:

zeromq-4.0.3/configure.ac:# Check polling system
zeromq-4.0.3/configure.ac:LIBZMQ_CHECK_POLLER([CPPFLAGS="${CPPFLAGS} -D${libzmq_cv_poller_flag}"],
zeromq-4.0.3/configure.ac: [AC_MSG_ERROR([Unable to continue without polling system])])

The actual checks in acinclude.m4 are the very same (diff zeromq-3.2.4/acinclude.m4 zeromq-4.0.3/acinclude.m4 prints no differences).