libc/glibc: fix downloading addons

Do to glibc what we did to eglibc in #dff359adf15c.

Only (very) old versions of glibc have other external addons,
and they are no longer meaningful.

But for consistency, do the change nonetheless.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

CT_EXPERIMENTAL=y

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_LOG_EXTRA=y

CT_ARCH_m68k=y

CT_KERNEL_linux=y

CT_KERNEL_V_3_5=y

CT_BINUTILS_V_2_21_1a=y

CT_LIBC_UCLIBC_CONFIG_FILE="${CT_LIB_DIR}/samples/${CT_TARGET}/${CT_LIBC}-${CT_LIBC_VERSION}.config"

CT_THREADS_LINUXTHREADS=y