Releases around mingw-w64 Toolchains targetting Win64/Personal Builds/mingw-builds/6.4.0/threads-win32/sjlj/x86_64-6.4.0-release-win32-sjlj-rt_v5-rev0.7z on SourceForge
Maybe you can find something interesting in this list
mingw-w64
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Toolchains targetting Win64/Personal Builds/mingw-builds/6.4.0/threads-win32/sjlj/x86_64-6.4.0-release-win32-sjlj-rt_v5-rev0.7z