[build.zig] Fix FileNotFound: .../src/raylib.h

[dylanlangston]

I'm getting an error when attempting to build using the latest raylib and Zig master (0.12.0-dev.3635+786876c05):

zig build -Dtarget=wasm32-emscripten
install
└─ install raylib failure
error: unable to update file from '.../src/raylib.h' to '.../zig-out/include/raylib.h': FileNotFound
Build Summary: 15/17 steps succeeded; 1 failed (disable with --summary none)
install transitive failure
└─ install raylib failure
error: the following build command failed with exit code 1:
.../zig-cache/o/8c0437471634c5f3da2ba2e71966fe50/build /home/vscode/.zvm/master/zig / .../zig-cache /home/vscode/.cache/zig --seed 0xbfa3d8ae -Z33b99a15b162f409 -Dtarget=wasm32-emscripten

As far as I can tell this isn't resolved by #3913 so I'm submitting this request.

To resolve I updated the LazyPath that raylib is importing its headers from with the current std.Build specified as the owner.

[raysan5]

@dylanlangston thanks for the review, merging...