Add Windows testing

.github/actions/mingw-configure.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+source mingw-env @TRIPLE@
+echo LAST IS: $last
+
+# check if last arg is a path to configure, else use parent
+for last; do true; done
+if test -x "${last}/configure"; then
+  config_path="$last"
+else
+  config_path=".."
+fi
+
+${config_path}/configure \
+  --host=@TRIPLE@ --target=@TRIPLE@ --build="$CHOST" \
+  --prefix=/usr/@TRIPLE@ --libdir=/usr/@TRIPLE@/lib --includedir=/usr/@TRIPLE@/include \
+  --enable-shared --enable-static "$@"