goto line :3938 and change
$text =~ s/\${([^ \t=:+{}]+)}/substitute_ac_subst_variables_worker ($1)/ge;
to
$text =~ s/\$\{([^ \t=:+\{\}]+)\}/substitute_ac_subst_variables_worker ($1)/ge;
vi ./build_dir/host/automake-1.15/bin/automake.in
goto line :3938 and change
$text =~ s/\${([^ \t=:+{}]+)}/substitute_ac_subst_variables_worker ($1)/ge;
to
$text =~ s/\$\{([^ \t=:+\{\}]+)\}/substitute_ac_subst_variables_worker ($1)/ge;
vi ./build_dir/host/automake-1.15/bin/automake.in