fixing miniaudio build issues for wasm target

[ekliot]

Matching the #+build directives to those in core:sys/posix

[gingerBill]

Why not just exclude wasm on those targets rather than explicitly adding everything else?

[ekliot]

@gingerBill I'm not clear what you're referring to with excluding wasm, but my reasoning for the changes:

• common_unix.odin imports posix, so it ought to only build on posix targets (rather than all of !windows)
• that leaves non-posix targets that need those typedefs (which are used elsewhere in the package), so I renamed common_windows.odin and added those exclusions so that windows, wasm, and other targets get the expected types (this seemed the most correct, if least elegant, option)

happy to adjust to another way to organize this.

perhaps to clarify the issue I'm trying to address: when building for wasm target, the posix and libc stuff gets included but is unavailable. so we need the wasm target to get those types when building, without missing or double-defining for other targets

[ekliot]

@gingerBill any word?