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)

# mingw options

# depends on MINGW32

config LIBC_mingw

    bool

    select LIBC_SUPPORT_WIN32THREADS

    help

      The de-facto standard for Mingw distributions.

choice

    bool

    prompt "Mingw runtime version"

# Don't remove next line

# CT_INSERT_VERSION_BELOW

config MINGWRT_V_3_18

    bool

    prompt "3.18"

config MINGWRT_V_select

    bool

    prompt "Other version"

endchoice

config MINGWRT_VERSION

    string

    prompt "Mingw runtime version" if MINGWRT_V_select

# Don't remove next line

# CT_INSERT_VERSION_STRING_BELOW

    default "3.18" if MINGWRT_V_3_18

    help

      Enter the version number of the mingw runtime files to use