libstdc++-6-pic-alpha-cross 6.5.0-2ubuntu1~18.04cross1 (arm64 binary) in ubuntu bionic

 This is used to develop subsets of the libstdc++ shared libraries for
 use on custom installation floppies and in embedded systems.
 .
 Unless you are making one of those, you will not need this package.
 .
 This package contains files for alpha architecture, for use in cross-compile
 environment.