w32: Fix PKG_CONFIG_LIBDIR in --build-w32

* autogen.sh: Point pkg-config to the right location.

--
PKG_CONFIG_LIBDIR is located to usually be /usr/lib/pkgconfig so
in our case it should also point directly to the pkgconfig location
and not the prefix. This fixes gnutls and sqlite detection.

Signed-off-by: Andre Heinecke <aheinecke@intevation.de>

autogen.sh

@@ -311,7 +311,7 @@ if [ "$myhost" = "w32" ]; then
     $tsdir/configure --enable-maintainer-mode ${SILENT} \
              --prefix=${w32root}  \
              --host=${host} --build=${build} SYSROOT=${w32root} \
-             PKG_CONFIG_LIBDIR=${w32root} \
+             PKG_CONFIG_LIBDIR=${w32root}/lib/pkgconfig \
              ${configure_opts} ${extraoptions} "$@"
     rc=$?
     exit $rc