libmicrohttpd: Building 0.9.24 fails on missing .texi files

Instead of a proper fix I am just tricking the build into completing.
After all, we don't care much about the documentation.

The actual error is:

    $ ./scripts/build libmicrohttpd
    ...
    rm -rf $backupdir; exit $rc
    libmicrohttpd.texi:2132: @include `lgpl.texi': No such file or directory.
    libmicrohttpd.texi:2136: @include `ecos.texi': No such file or directory.
    libmicrohttpd.texi:2140: @include `fdl-1.3.texi': No such file or directory.
    makeinfo: Removing output file `libmicrohttpd.info' due to errors; use --force to preserve.
    make[1]: *** [libmicrohttpd.info] Error 1