scripts: leave changelog in build dir, copy to install dir

Users tend to look for the build log in the current working directory,
rather than in the toolchain's installation dir. While bundling the build
log in the toolchain installation dir is nice for distribution and review,
it can be easier to have the build log readily available in the working
directory, as it is quicker to get to it.

So, the build log stays in the working directory until the toolchain is
completely and successfully built, and then a (compressed) copy is made.

Reported-by: Trevor Woerner <twoerner@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# 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