coreboot filesystem tool does not build

[wwwutz]

build fails as user build:

    HOSTCC     cbfstool/linux_trampoline.o
    HOSTCC     cbfstool/cbfs-payload-linux.o
    HOSTCC     cbfstool/fmaptool.o
/scratch/local2/beehive/cbfstool-4.5.474_g91bfa8e-0/buildroot/cbfstool/cbfstool-4.5.474_g91bfa8e-0/source/util/cbfstool/lz4/lib/lz4frame.c: In function ‘LZ4F_decompress’:
/scratch/local2/beehive/cbfstool-4.5.474_g91bfa8e-0/buildroot/cbfstool/cbfstool-4.5.474_g91bfa8e-0/source/util/cbfstool/lz4/lib/lz4frame.c:1092:33: error: this statement may fall through [-Werror=implicit-fallthrough=]
                 dctxPtr->dStage = dstage_storeHeader;
                 ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
/scratch/local2/beehive/cbfstool-4.5.474_g91bfa8e-0/buildroot/cbfstool/cbfstool-4.5.474_g91bfa8e-0/source/util/cbfstool/lz4/lib/lz4frame.c:1095:9: note: here
         case dstage_storeHeader:
         ^~~~
    HOSTCC     cbfstool/cbfs_sections.o
    HOSTCC     cbfstool/fmap_from_fmd.o

see: /src/mariux/beehive/work/cbfstool-4.5.474_g91bfa8e-0.stdout