On CI it is nice to cache the external dependencies. However if we
always compile them in the same folder we cannot cache for multiple
different architectures. After this commit native compile targets will
still live in `external` but cross compiled versions will live in
`external/<arch>`.
* remove libbase58, use base58 from libwally
This removes libbase58 and uses libwally instead.
It allocates and then frees some memory, we may want to
add a function in wally that doesn't or override
wally_operations to use tal.
Signed-off-by: Lawrence Nahum lawrence@greenaddress.it
