fix migration to 0.13.0 errors

build.zig

@@ -16,7 +16,7 @@ pub fn build(b: *std.Build) void {
     const optimize = b.standardOptimizeOption(.{});
 
     _ = b.addModule("zigdeck", .{
-        .root_source_file = .{ .path = "lib.zig" },
+        .root_source_file = b.path("lib.zig" ),
         .target = target,
         .optimize = optimize,
      });
@@ -25,7 +25,7 @@ pub fn build(b: *std.Build) void {
         .name = "zigdeck",
         // In this case the main source file is merely a path, however, in more
         // complicated build scripts, this could be a generated file.
-        .root_source_file = .{ .path = "lib.zig" },
+        .root_source_file = b.path("lib.zig"),
         .target = target,
         .optimize = optimize,
     });
@@ -39,7 +39,7 @@ pub fn build(b: *std.Build) void {
     // Creates a step for unit testing. This only builds the test executable
     // but does not run it.
     const lib_unit_tests = b.addTest(.{
-        .root_source_file = .{ .path = "lib.zig" },
+        .root_source_file = b.path("lib.zig"),
         .target = target,
         .optimize = optimize,
     });