I cannot disable GCC TLS support thoroughly.

[Terry Guo]

Hello,

I configured my gcc with "--disable-tls" for arm-none-eabi. But it can
still successfully compile the below case:

  __thread int i;
        int f (void) { return i; }
        void main (int j) { i = j; }

The "dg-require-effective-target tls" use this case to check whether
target supports tls. So how to configure GCC to let it fail to compile
this case, and then let the dg test framework thinks the tls is
unsupported? Thanks in advance.

BR,
Terry