Did you take a look at the C++ implementation of the hashing function they did? I didn't see a single call made there. They replaced python code that makes 5 calls into a single call.
That's a copy-pasted variation of this public-domain SHA1 code: http://ftp.funet.fi/pub/crypt/hash/sha/sha1.c surrounded by base64 decoding and encoding for a known-length binary text.
By inlining all library code you use, yes indeed, you too can also not make a single call.
By inlining all library code you use, yes indeed, you too can also not make a single call.