This document describes how libicuio was packaged for build2. In particular,
this understanding will be useful when upgrading to a new upstream version.
See ../README-DEV for general notes on ICU packaging.

Symlink the required upstream files and directories into libicuio/io/ and
apply a patch that fixes the 'unable to find numeric literal operator' GCC 11
error:

$ mkdir libicuio/io
$ pushd libicuio/io
$ ln -s ../../../upstream/icu4c/source/io/{*.{h,cpp},unicode} ./
$ rm ufile.cpp
$ cp ../../../upstream/icu4c/source/io/ufile.cpp ./
$ git apply ufile.cpp.patch
$ popd

Note that the patch is produces by the following command:

$ git diff >ufile.cpp.patch