Revert to using --enable-auto-import in Cygwin builds.
Revert to using --enable-auto-import in Cygwin builds.

Disabling auto-import requires that all libraries we use be careful about
declspecs for exported variables; and it seems they aren't.  This means
that Cygwin will not give us useful info about missing PGDLLIMPORT markers;
but it's probably sufficient that MSVC and Mingw builds do.

oberstet/postgres-xl,Postgres-XL/Postgres-XL,greenplum-db/gpdb,ovr/postgres-xl,50wu/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,pavanvd/postgres-xl,ovr/postgres-xl,Postgres-XL/Postgres-XL,ashwinstar/gpdb,xinzweb/gpdb,techdragon/Postgres-XL,ovr/postgres-xl,adam8157/gpdb,zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl,50wu/gpdb,pavanvd/postgres-xl,50wu/gpdb,50wu/gpdb,50wu/gpdb,techdragon/Postgres-XL,50wu/gpdb,jmcatamney/gpdb,yazun/postgres-xl,adam8157/gpdb,50wu/gpdb,50wu/gpdb,oberstet/postgres-xl,zeroae/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,xinzweb/gpdb,xinzweb/gpdb,yazun/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,ashwinstar/gpdb,lisakowen/gpdb,lisakowen/gpdb,pavanvd/postgres-xl,ashwinstar/gpdb,adam8157/gpdb,yazun/postgres-xl,lisakowen/gpdb,xinzweb/gpdb,jmcatamney/gpdb,lisakowen/gpdb,ashwinstar/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,oberstet/postgres-xl,pavanvd/postgres-xl,zeroae/postgres-xl,adam8157/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,Postgres-XL/Postgres-XL,jmcatamney/gpdb,xinzweb/gpdb,techdragon/Postgres-XL,yazun/postgres-xl,lisakowen/gpdb,oberstet/postgres-xl,adam8157/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,lisakowen/gpdb,adam8157/gpdb,Postgres-XL/Postgres-XL,ovr/postgres-xl,techdragon/Postgres-XL,greenplum-db/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,yazun/postgres-xl,greenplum-db/gpdb,pavanvd/postgres-xl,adam8157/gpdb,greenplum-db/gpdb,ovr/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,jmcatamney/gpdb