libc/glibc: fix {e,}glibc add-ons with short or long names

Fixes the issue with {e,}glibc addons having short and long names (such as
eglibc-ports-2_13 and ports), which caused configure scripts to run
through them twice and thus configuring incorrectly.

For instance, the mips64el-n32-linux-gnu toolchain would be recognized
correctly first, but then the second pass would change it to mips32,
building a mixed MIPS-III N32 and MIPS-I libc.

Signed-off-by: Nicolás Reynolds <fauno@kiwwwi.com.ar>
[yann.morin.1992@anciens.enib.fr: remove spurious trailing spaces]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from af25723a794f2017f45c300369a6d36849e22236)

# MIPS specific config options

choice

    bool

    prompt "ABI"

config ARCH_mips_o32

    bool

    prompt "o32"

    depends on ARCH_32

    help

      This is the -mabi=32 gcc option.

config ARCH_mips_n32

    bool

    prompt "n32"

    depends on ARCH_64

    help

      This is the -mabi=n32 gcc option.

config ARCH_mips_n64

    bool

    prompt "n64"

    depends on ARCH_64

    help

      This is the -mabi=64 gcc option.

# Not supported on Linux:

# o64   : seems related to *BSD

# eabi  : seems related to bare-metal

endchoice

config ARCH_mips_ABI

    string

    default "32"    if ARCH_mips_o32

    default "n32"   if ARCH_mips_n32

    default "64"    if ARCH_mips_n64