Add wrap for native SoftFloat subproject and use the native dep

[DMaroo]

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• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• I've added tests that prove my fix is effective or that my feature works (if possible)
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Detailed description

The top-level meson file now uses the native SoftFloat dependency is the project is being cross-compiled. Using the cross-native branch of SoftFloat for native subproject. This ought to fix the issue raised in #4604 (comment).

To understand why this works, have a look at this commit.

Test plan

Android build should be green.

Closing issues

Related PR: #4593.

[DMaroo]

Sending it from a dist- branch.