1.18: type "filenamehere" not found

Input:

```
» cat x.c
#include <stdio.h>
int main()
{
        fprintf(stderr, "hi world\n");
        return 0;
}
» gcc x.c -Wall -ggdb3
» strip -s a.out
```

Observed behavior (pahole 1.18):

```
» pahole ./a.out 
pahole: type './a.out' not found
»
```

Expected behavior (like pahole 1.17):

```
» pahole a.out 
»
```