tests: add 'aligned_attr_gcc_windows.vv' for gcc (#20870)

vlib/v/gen/c/coutput_test.v

@@ -255,6 +255,12 @@ fn should_skip(relpath string) bool {
 				return true
 			}
 		}
+		$if msvc {
+			if relpath.contains('_gcc_windows.vv') {
+				eprintln('> skipping ${relpath} on msvc')
+				return true
+			}
+		}
 	} else {
 		if relpath.contains('_windows.vv') {
 			eprintln('> skipping ${relpath} on !windows')

vlib/v/gen/c/testdata/aligned_attr_gcc_windows.c.must_have

@@ -0,0 +1,13 @@
+
+struct main__Test {
+	int a;
+}  __attribute__((aligned (8)));
+
+struct main__Test2 {
+	int a;
+	int b;
+}  __attribute__((aligned (16)));
+
+union main__Test3 {
+	int a;
+}  __attribute__((aligned (8)));

vlib/v/gen/c/testdata/aligned_attr_gcc_windows.vv

@@ -0,0 +1,17 @@
+// vtest vflags: -cc gcc -os windows
+
+@[aligned:8]
+struct Test {
+	a int
+}
+
+@[aligned:16]
+struct Test2 {
+	a int 
+	b int
+}
+
+@[aligned:8]
+union Test3 {
+	a int
+}