build-mingw-w64: Update to the latest version from git

This version includes libucrtapp.a, which doesn't require linking to
vcruntime140_app for avoiding api-ms-win-crt-private-*.dll.

build-mingw-w64.sh

@@ -18,7 +18,7 @@ set -e
 
 : ${DEFAULT_WIN32_WINNT:=0x601}
 : ${DEFAULT_MSVCRT:=ucrt}
-: ${MINGW_W64_VERSION:=bb73d2e3a260d20e72fe4221411032f4175f58ec}
+: ${MINGW_W64_VERSION:=76e56e6fb70d3a21e054c2c0de8822c108807d28}
 unset HOST
 
 while [ $# -gt 0 ]; do