Deprecated LazyPath breaks with Zig master

[SlaktarMicke92]

In Zig master, changes have been made to setting paths in build files, example:

.root_source_file = b.path("src/main.zig"),

Zap still uses the old way to do it, which results in the error given under Actual.

Actual

error: no field named 'path' in union 'Build.LazyPath'
        .root_source_file = .{ .path = "src/zap.zig" },

Expected

Build runs without errors

Source

The fix needed for this should not break in Zig 0.12:

https://ziglang.org/download/0.12.0/release-notes.html#introduce-bpath-deprecate-LazyPathrelative

Suggestion

Replace all .{ .path = "path/to/file.zig" }, to b.path("src/main.zig"), in build.zig for both Zap and facil.io

[SlaktarMicke92]

Created a pull request: #105