lib64stdc++6-x32-cross 8.4.0-1ubuntu1~18.04cross1 (i386 binary) in ubuntu bionic

 This package contains an additional runtime library for C++ programs
 built with the GNU compiler.
 .
 libstdc++-v3 is a complete rewrite from the previous libstdc++-v2, which
 was included up to g++-2.95. The first version of libstdc++-v3 appeared
 in g++-3.0.
 .
 This package contains files for x32 architecture, for use in cross-compile
 environment.