libgcc: use the new recipe (rather than gcc-runtime) to install libgcc_s.so* and crt*.o
Currently gcc-runtime installs the files, but actually gcc-runtime's
do_configure checks if the files are available, so before we build gcc-runtime,
we should have some recipe install the files first! -- currently
gcc-cross-intermediate actually does that(gcc-cross also installs the files,
but it installs into the gcc-build-internal* directory), but
gcc-cross-intermediate will have its own sysroot in future, after that,
gcc-runtime won't build. So let us add this new target recipe and move the
installation of the files from gcc-runtime into it.
