Add LoongArch basic support

[lixing-star]

Dear maintainers, I'd like to add one new architecture support for LoongArch. The document and code we've already supported list as follow: https://loongson.github.io/LoongArch-Documentation/README-EN.html https://github.com/loongson

And we tested libcds on 3A6000 cpu with firebird links follow, https://github.com/FirebirdSQL/firebird/pull/7531

Waiting for your reply, thanks

[TomlyYang]

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[lixing-star]

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Dear maintainers, how about this PR? We've already tested on Loongson-3A6000 with all of the test passed as mentioned in https://github.com/FirebirdSQL/firebird/pull/7531

thanks.

[TomlyYang]

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