Fix URL for downloading released Windows MSYS binaries.
Fix URL for downloading released Windows MSYS binaries.

Change-Id: Id45bc1bcfb4b9ba5180482e0a810e82fc983f0ca

bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration