%%% src_config
As in \Prog{pass1-gcc}, additionally replace \File{lib64} with \File{lib}:

\begin{verbatim}
    -e "s@/lib64@/lib@g" \
\end{verbatim}

Pass macros \texttt{HAVE_DECL_VASPRINTF} to configure:
\begin{verbatim}
    CFLAGS="-DHAVE_DECL_VASPRINTF=1"                   \
    CXXFLAGS="-DHAVE_DECL_VASPRINTF=1"                 \
\end{verbatim}

\File{include/libiberty.h} contains its own prototype of function \Arg{vasprintf}, which is incompatible with
system prototype from \Prog{glibc}, located in file \Envar{\$PREFIX}\File{/include/stdio.h}.
At minimum, versions \Arg{glibc-2.27} and higher are incompatible.

\Prog{gcc-7} and \Prog{gcc-8} ignore the incompatibility, but our self-built \Prog{pass1-gcc-9} does not.
That results in multiple failures during configuration tests of \Prog{pass2-gcc} and the further build is screwed.

The macros above turns off the usage of prototype variant from \File{include/libiberty.h}.

Why \Prog{gcc-9} does not handle the situation with \Arg{vasprintf} itself? That't unclear.
