E.g. nix-instantiate --eval -E 'abort "\r"' hangs.

Found by afl-fuzz.

Otherwise, running e.g.

nix-instantiate --eval -E --strict 'builtins.replaceStrings [""] ["X"] "abc"'

would just hang in an infinite loop.

Found by afl-fuzz.

The assertion is broken because there is no one-to-one mapping from
length of a base64 string to the length of the output.

E.g.

"1q69lz7Empb06nzfkj651413n9icx0njmyr3xzq1j9q=" results in a 32-byte output.
"1q69lz7Empb06nzfkj651413n9icx0njmyr3xzq1j9qy" results in a 33-byte output.

To reproduce, evaluate:

builtins.derivationStrict {
    name = "0";
    builder = "0";
    system = "0";
    outputHashAlgo = "sha256";
    outputHash = "1q69lz7Empb06nzfkj651413n9icx0njmyr3xzq1j9qy";
}

Found by afl-fuzz.