enable PIC for multi-versioned objects when targeting shared libraries

[0xroko]

addMultiVersion objects don't inherit PIC from the parent compile step. When linking into a dynamic library, the linker fails with R_X86_64_32S relocation cannot be used against local symbol. This auto-detects compile.linkage == .dynamic and sets .pic = true on both the user and wrapper modules, with an explicit override option.

[ATTron]

Hey, thanks for this :) great catch and clean fix!

Tested locally on macOS aarch64 (Zig 0.16.0). Build and tests pass. The example hits a PIC error, but that's already broken on main so not from your PR :)

One thing — compile.linkage == .dynamic misses platforms like macOS/aarch64 where PIC is required for everything. Swapping to compile.root_module.pic inherits what Zig already decided for the parent, covering both cases. Tested and the example runs clean after that ( i should probably make it CI tbh but another task for another day )

I'll push the tweak onto your branch. Thanks for helping out!