x86_64 builds of mingw32 are not supported directly and should just configure as generic mingw32 builds since they're NOT 64 bit.
diff --git a/configure.ac b/configure.ac
index 8010e11..c8f4540 100644
--- a/configure.ac
+++ b/configure.ac
@@ -79,13 +79,6 @@ case $target in
esac
case $target in
- x86_64-w64-mingw32)
- have_x86_64=true
- have_win32=true
- PTHREAD_FLAGS=""
- DLOPEN_FLAGS=""
- WS2_LIBS="-lws2_32"
- ;;
*-*-mingw*)
have_x86_64=false
have_win32=true