[CN-Exec] Spacing and for-loops cause source injection errors

[dc-mak]

15:39 ➜  VST git:(VST) ✗ cat tmp.c
int main()
{
    int sum = 0;
    for (int i=0; i<10; i++) {
        sum += i;
    }
    return (sum - sum + 2*sum - sum - sum);
}

15:39 ➜  VST git:(VST) ✗ /home/dhruv/.opam/4.14.1/lib/cn/runtime/libexec/cn-runtime-single-file.sh -o tmp.c
Generating C files from CN-annotated source.
./tmp-exec.c: In function ‘main’:
./tmp-exec.c:18:19: error: expected identifier or ‘(’ before ‘signed’
   18 | signed int i = 0, signed int a_687 = c_add_local_to_ghost_state((uintptr_t) &i, sizeof(signed int)), 0;
      |                   ^~~~~~
Failed to compile C files in /tmp/cn-exec.o6f3.