lib/init-exe, lib/init-lib: ensure tests runs again

After commit ede5dcf (make the build runner and test runner talk to each other),
the std.Build.addTest function no longer runs tests, but the build.zig
files in init-exe and init-lib where not updated.

Rename main_tests to lib_tests in init-lib, for consistency with the
exe_tests variable in init-exe.

Add a RunStep to exe_tests and lib_tests.

Remove an empty line in the addCliTests function in tests/tests.zig.

Closes #15009

Author: perillo

lib/init-exe/build.zig

@@ -63,5 +63,5 @@ pub fn build(b: *std.Build) void {
     // the `zig build --help` menu, providing a way for the user to request
     // running the unit tests.
     const test_step = b.step("test", "Run unit tests");
-    test_step.dependOn(&exe_tests.step);
+    test_step.dependOn(&exe_tests.run().step);
 }

lib/init-lib/build.zig

@@ -30,7 +30,7 @@ pub fn build(b: *std.Build) void {
     lib.install();
 
     // Creates a step for unit testing.
-    const main_tests = b.addTest(.{
+    const lib_tests = b.addTest(.{
         .root_source_file = .{ .path = "src/main.zig" },
         .target = target,
         .optimize = optimize,
@@ -40,5 +40,5 @@ pub fn build(b: *std.Build) void {
     // and can be selected like this: `zig build test`
     // This will evaluate the `test` step rather than the default, which is "install".
     const test_step = b.step("test", "Run library tests");
-    test_step.dependOn(&main_tests.step);
+    test_step.dependOn(&lib_tests.run().step);
 }

test/tests.zig

@@ -663,7 +663,6 @@ pub fn addCliTests(b: *std.Build) *Step {
     const s = std.fs.path.sep_str;
 
     {
-
         // Test `zig init-lib`.
         const tmp_path = b.makeTempPath();
         const init_lib = b.addSystemCommand(&.{ b.zig_exe, "init-lib" });