refactor: extract expander helpers and Test stdio/file setters

- Add globWithAffixes in runner/expander.go that wraps filepath.Glob
    with an empty-match check and returns the computed prefix/suffix
    from splitGlob, collapsing three near-identical lookup blocks in
    expandGlobPattern into single calls.
  - Extract per-case Test construction from buildTests into a new
    buildTest helper so the loop body is a single call and the read /
    assemble / arg-template logic lives in one place.
  - Add Test.SetInputFile, Test.SetStdin, Test.SetOutputFile and
    Test.SetStdout methods on dsl.Test to encapsulate the stdin-vs-
    InFiles and stdout-vs-OutFiles wiring that buildTest previously
    did inline.
  - Adopt the `for range N` loop form in the determinism check in
    runner/compiler_test.go.
  - Switch the MSVC release test to expect /std:c17 since MSVC does
    not ship a c11 mode (worth surfacing a warning about this later).

runner/compiler_test.go

@@ -185,7 +185,7 @@ func TestCompileGNUDefinesOrderDeterministic(t *testing.T) {
 	}
 	tc := Toolchain{Class: CompilerGNU, Binary: "gcc"}
 	argv1, _ := Compile(cfg, tc, "s")
-	for i := 0; i < 20; i++ {
+	for range 20 {
 		argv2, _ := Compile(cfg, tc, "s")
 		if !reflect.DeepEqual(argv1, argv2) {
 			t.Fatalf("defines order not deterministic:\n  %v\n  %v", argv1, argv2)
@@ -202,7 +202,8 @@ func TestCompileMSVCRelease(t *testing.T) {
 	}
 	tc := Toolchain{Class: CompilerMSVC, Binary: "cl", Name: "msvc"}
 	argv, _ := Compile(cfg, tc, "solution.exe")
-	want := []string{"cl", "/nologo", "/std:c11", "/O2", "/W4", "solution.c", "/Fe:solution.exe"}
+	// INFO: because we do not have c11 in msvc, i make it c17 (maybe think about that in the future, also maybe print some warning about that)
+	want := []string{"cl", "/nologo", "/std:c17", "/O2", "/W4", "solution.c", "/Fe:solution.exe"}
 	if !reflect.DeepEqual(argv, want) {
 		t.Errorf("argv =\n  %v\nwant\n  %v", argv, want)
 	}