I searched a little bit arround and found this: https://web.archive.org/web/20210506222114/https://git.kernel.org/pub/scm/linux/kernel/git/cjb/mmc-utils.git/ and I found this: https://kernel.googlesource.com/pub/scm/utils/mmc/mmc-utils/ If you search for example in web.archive: mmc_cmds.c: fix build with gcc 4.9 you will also find this on the googlesource. I do not know if it helps to build a kernal for this points but I put it here.