Samuel Holland authored Jan 20, 2019 and Marge Bot committed Jan 21, 2019

GHC has code to handle unsuffixed .so files that are linker scripts
pointing to the real shared library. The detection is done by parsing
the result of `dlerror()` after calling `dlopen()` and looking for
certain error strings. On musl libc, the error message is "Exec format
error", which happens to be `strerror(ENOEXEC)`:

```
$ cat tmp.c
#include <dlfcn.h>
#include <stdio.h>

int main(void) {
        dlopen("libz.so", RTLD_NOW | RTLD_GLOBAL);
        puts(dlerror());
        return 0;
}
$ gcc -o tmp tmp.c
$ ./tmp
Error loading shared library libz.so: Exec format error
$
```

This change fixes the workaround to also work on musl libc.

Link: https://phabricator.haskell.org/D5474