Downgrade to mingw-w64 10.0.0 in Windows toolchain.

Makefile

@@ -76,6 +76,8 @@ toolchain-win := $(LOCAL_DIR)/x86_64-w64-mingw32
 toolchain-win: $(toolchain-win)
 $(toolchain-win): $(crosstool-ng)
 	ct-ng x86_64-w64-mingw32
+	# I don't know how to set crosstool-ng variables from the command line
+	sed -i 's/CT_MINGW_W64_VERSION=.*/CT_MINGW_W64_VERSION="v10.0.0"/' .config
 	CT_PREFIX="$(LOCAL_DIR)" ct-ng build$(JOBS_CT_NG)
 	rm -rf .build .config build.log