Avoid calling back() on an empty string in setBinaryenBinDir (#5280)

std::string::back() is only well defined for non-empty strings.
Without the change, wasm-reduce fails if it is called from
$PATH, because then, the parent directory is an empty string.
A workaround is to explicitly set the binaryen path with -b,
and it is still necessary after this fix, but at least the program
ends with a comprehensible error message instead of a generic
assertion failure from the standard library.

0 files changed, 0 insertions, 0 deletions