[Clang] [Tests] Add some more tests around non-local/non-variable declarations in C for loops (#131199)

As requested by @shafik in
#129737 (comment).
I also added a test for `thread_local` because why not.

Author: Sirraide

clang/test/Sema/for.c

@@ -5,17 +5,19 @@
 void b1 (void) { for (void (*f) (void);;); }
 void b2 (void) { for (void f (void);;); }   /* c11-warning {{non-variable declaration in 'for' loop is a C23 extension}}
                                                c23-warning {{non-variable declaration in 'for' loop is incompatible with C standards before C23}} */
-void b3 (void) { for (static int f;;); }    /* c11-warning {{declaration of non-local variable in 'for' loop is a C23 extension}}
-                                               c23-warning {{declaration of non-local variable in 'for' loop is incompatible with C standards before C23}} */
+void b3 (void) { for (static int f;f;); }    /* c11-warning {{declaration of non-local variable in 'for' loop is a C23 extension}}
+                                                c23-warning {{declaration of non-local variable in 'for' loop is incompatible with C standards before C23}} */
 
 void b4 (void) { for (typedef int f;;); }   /* c11-warning {{non-variable declaration in 'for' loop is a C23 extension}}
                                                c23-warning {{non-variable declaration in 'for' loop is incompatible with C standards before C23}} */
-void b5 (void) { for (struct { int i; } s;;); }
-void b6 (void) { for (enum { zero, ten = 10 } i;;); }
+void b5 (void) { for (struct { int i; } s;s.i;); }
+void b6 (void) { for (enum { zero, ten = 10 } i = ten;i;); }
 void b7 (void) { for (struct s { int i; };;); } /* c11-warning {{non-variable declaration in 'for' loop is a C23 extension}}
                                                    c23-warning {{non-variable declaration in 'for' loop is incompatible with C standards before C23}} */
-void b8 (void) { for (static struct { int i; } s;;); } /* c11-warning {{declaration of non-local variable in 'for' loop is a C23 extension}}
-                                                          c23-warning {{declaration of non-local variable in 'for' loop is incompatible with C standards before C23}} */
-void b9 (void) { for (struct { int i; } (*s)(struct { int j; } o) = 0;;); }
+void b8 (void) { for (static struct { int i; } s;s.i;); } /* c11-warning {{declaration of non-local variable in 'for' loop is a C23 extension}}
+                                                             c23-warning {{declaration of non-local variable in 'for' loop is incompatible with C standards before C23}} */
+void b9 (void) { for (struct { int i; } (*s)(struct { int j; } o) = 0;s;); }
 void b10(void) { for (typedef struct { int i; } (*s)(struct { int j; });;); } /* c11-warning {{non-variable declaration in 'for' loop is a C23 extension}}
                                                                                  c23-warning {{non-variable declaration in 'for' loop is incompatible with C standards before C23}} */
+void b11 (void) { for (static _Thread_local struct { int i; } s;s.i;); } /* c11-warning {{declaration of non-local variable in 'for' loop is a C23 extension}}
+                                                                            c23-warning {{declaration of non-local variable in 'for' loop is incompatible with C standards before C23}} */