build-mingw-w64: Bump to the almost latest version as of Feb 3rd

Skipping the topmost two commits, as they are known to cause
problems building Firefox.

Author: mstorsjo

build-mingw-w64.sh

@@ -18,7 +18,7 @@ set -e
 
 : ${DEFAULT_WIN32_WINNT:=0x601}
 : ${DEFAULT_MSVCRT:=ucrt}
-: ${MINGW_W64_VERSION:=03d8a40f57649fbb773f1cdbe3a760f5e0943e76}
+: ${MINGW_W64_VERSION:=be91da60c4ae62a76099279500810c8ffbef4da1}
 
 CFGUARD_FLAGS="--enable-cfguard"