Fix for adding the `table-helper` package in chapter 3 (Build system)

[glennyonemitsu]

In both Zig 0.8 and master this didn't comply with the API.

[Sobeston]

This API usage still works in master

[glennyonemitsu]

I might be misunderstanding something, but this did not for me.

$../zig version
0.9.0-dev.952+0c091feb5

$cat build.zig
const std = @import("std");

pub fn build(b: *std.build.Builder) void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});

    // Standard release options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall.
    const mode = b.standardReleaseOptions();

    const exe = b.addExecutable("p", "src/main.zig");
    exe.setTarget(target);
    exe.setBuildMode(mode);

    exe.addPackage(.{
        .name = "table-helper",
        .path = "libs/table-helper/table-helper.zig",
    });

    exe.install();

    const run_cmd = exe.run();
    run_cmd.step.dependOn(b.getInstallStep());
    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);
}

$../zig build
./build.zig:20:17: error: expected type 'std.build.FileSource', found '*const [34:0]u8'
        .path = "libs/table-helper/table-helper.zig",
                ^
<omitted>:1355:24: note: std.build.FileSource declared here
pub const FileSource = union(enum) {
                       ^

What made this API method work for me is this (or the diff in this PR):

    exe.addPackage(.{
        .name = "table-helper",
        .path = std.build.FileSource{ .path = "libs/table-helper/table-helper.zig" },
    });

[Sobeston]

Sorry you were totally right, I misread the diff.

[glennyonemitsu]

I see now how my PR might have just been seen as a pointless method switch.

Thank you for reconsidering my PR and accepting it.