Comment 61 for bug 1740892

Was able to build fine using (optional)

--------------------
Standard symbol tags

optional

A symbol marked as optional can disappear from the library at any time and that will never cause dpkg-gensymbols to fail. However, disappeared optional symbols will continuously appear as MISSING in the diff in each new package revision. This behaviour serves as a reminder for the maintainer that such a symbol needs to be removed from the symbol file or readded to the library. When the optional symbol, which was previously declared as MISSING, suddenly reappears in the next revision, it will be upgraded back to the “existing” status with its minimum version unchanged.

This tag is useful for symbols which are private where their disappearance do not cause ABI breakage. For example, most of C++ template instantiations fall into this category. Like any
other tag, this one may also have an arbitrary value: it could be used to indicate why the symbol is considered optional.
--------------------