build: extract example executable from default target

build.zig

@@ -20,14 +20,17 @@ pub fn build(b: *std.Build) void {
         .optimize = optimize,
     });
 
-    const exe = b.addExecutable(.{
+    const example_step = b.step("example", "build example");
+
+    const ex_exe = b.addExecutable(.{
         .name = "yamltest",
-        .root_source_file = .{ .path = "src/main.zig" },
+        .root_source_file = .{ .path = "example/main.zig" },
         .target = target,
         .optimize = optimize,
     });
-    exe.linkLibrary(libyaml);
+    ex_exe.linkLibrary(libyaml);
-    exe.addModule("yaml", yaml_zig);
+    ex_exe.addModule("yaml", yaml_zig);
 
-    b.installArtifact(exe);
+    const install = b.addInstallArtifact(ex_exe, .{});
+    example_step.dependOn(&install.step);
 }

example/main.zig

@@ -7,11 +7,14 @@ pub fn main() !void {
     defer _ = gpa.deinit();
     const allocator = gpa.allocator();
 
-    const slurp = try std.fs.cwd().readFileAlloc(
+    const slurp = std.fs.cwd().readFileAlloc(
         allocator,
         "test.yaml",
         1024 * 1024 * 1024,
-    );
+    ) catch |err| {
+        std.debug.print("couldn't open test.yaml in the cwd\n", .{});
+        return err;
+    };
     defer allocator.free(slurp);
 
     var diag = yaml.ParseDiagnostic{ .message = "?????" };