AstGen: fix loop control flow applying to wrong loop

In the case of 'continue' or 'break' inside the 'else' block of a
'while' or 'for' loop.

Closes #12109

test/behavior/for.zig

@@ -210,3 +210,17 @@ test "for on slice with allowzero ptr" {
     try S.doTheTest(&[_]u8{ 1, 2, 3, 4 });
     comptime try S.doTheTest(&[_]u8{ 1, 2, 3, 4 });
 }
+
+test "else continue outer for" {
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+
+    var i: usize = 6;
+    var buf: [5]u8 = undefined;
+    while (true) {
+        i -= 1;
+        for (buf[i..5]) |_| {
+            return;
+        } else continue;
+    }
+}

test/behavior/while.zig

@@ -334,3 +334,13 @@ test "continue inline while loop" {
     }
     comptime assert(i == 5);
 }
+
+test "else continue outer while" {
+    var i: usize = 0;
+    while (true) {
+        i += 1;
+        while (i > 5) {
+            return;
+        } else continue;
+    }
+}