mbsync with XOAUTH2 SASL mechanism

[Peter Polidoro]

I am trying to setup an oauth2 email account to work with Emacs 
using mbsync (from the isync guix package) and mu4e.

I setup oauth2ms to fetch the token and setup mbsync to use 
oauth2ms for the PassCmd and XOAUTH2 for the AuthMechs.

Now when I run mbsync, I get the error:

IMAP error: selected SASL mechanism(s) not available;
  selected: XOAUTH2
  available: SCRAM-SHA-1 SCRAM-SHA-256 GS2-IAKERB GS2-KRB5 GSSAPI 
  GSS-SPNEGO DIGEST-MD5 EXTERNAL OTP CRAM-MD5 PLAIN ANONYMOUS

I found instructions online saying I need to install the xoauth2 
sasl plugin from https://github.com/moriyoshi/cyrus-sasl-xoauth2

What is the proper Guix way of getting mbsync to work with 
XOAUTH2? Should I try to package cyrus-sasl-xoauth2 or modify the 
isync package or something else? Thanks!