libc/eglibc: fix downloading of localedef addon

For the versions of eglibc where the ports addon is not external (ie,
all versions after, and including 2.17), we would fail to download the
localedef addon, since the test did not care about the addon we were
about to download, only whether the ports addon was external or not.

Fix that by skipping the ports addon only if that's the addon we're
trying to download.

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

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_LOG_EXTRA=y

CT_ARCH_LE=y

CT_ARCH_FLOAT_SW=y

CT_ARCH_mips=y

CT_TARGET_VENDOR="sde"

CT_BINUTILS_V_2_21_1a=y

CT_CC_V_4_4_6=y

# CT_CC_GCC_ENABLE_TARGET_OPTSPACE is not set

CT_LIBC_none=y

CT_DEBUG_gdb=y

CT_GDB_V_6_8a=y

CT_GMP_V_4_3_2=y

CT_MPFR_V_2_4_2=y

CT_PPL_V_0_10_2=y

CT_CLOOG_V_0_15_10=y