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_EXPERIMENTAL=y

 CT_LOCAL_TARBALLS_DIR="${HOME}/src"

 CT_SAVE_TARBALLS=y

 CT_LOG_EXTRA=y

 CT_ARCH_mips=y

 CT_TARGET_VENDOR="malta"

 CT_KERNEL_linux=y

 CT_KERNEL_V_2_6_38=y

 CT_BINUTILS_V_2_21_1a=y

 CT_CC_V_4_4_6=y

 # CT_CC_GCC_USE_GRAPHITE is not set

 CT_LIBC_EGLIBC_V_2_13=y

 CT_DEBUG_gdb=y

 # CT_GDB_GDBSERVER_STATIC is not set

 CT_GDB_V_7_2a=y

 CT_GMP_V_5_0_1=y

 CT_MPFR_V_3_0_0=y

 CT_TEST_SUITE_GCC=y