autobuild: Fix two issues

The test for defining the automake conditional for the poll
implementation was keying off of the threads variable, producing
incorrect results for Cygwin.

A simple typo in the Makefile causes a build failure when
cross-compiling for Windows.

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>
diff --git a/configure.ac b/configure.ac
index 4b8752a..a273688 100644
--- a/configure.ac
+++ b/configure.ac
@@ -186,8 +186,8 @@
 AM_CONDITIONAL([OS_OPENBSD], [test "x$backend" = xopenbsd])
 AM_CONDITIONAL([OS_SUNOS], [test "x$backend" = xsunos])
 AM_CONDITIONAL([OS_WINDOWS], [test "x$backend" = xwindows])
-AM_CONDITIONAL([POLL_POSIX], [test "x$threads" = xposix])
-AM_CONDITIONAL([POLL_WINDOWS], [test "x$threads" = xwindows])
+AM_CONDITIONAL([POLL_POSIX], [test "x$poll" = xposix])
+AM_CONDITIONAL([POLL_WINDOWS], [test "x$poll" = xwindows])
 AM_CONDITIONAL([THREADS_POSIX], [test "x$threads" = xposix])
 AM_CONDITIONAL([THREADS_WINDOWS], [test "x$threads" = xwindows])
 AM_CONDITIONAL([CREATE_IMPORT_LIB], [test "x$create_import_lib" = xyes])