This tool will remove old versions of NVRAM NVAR non-volatile
variables and leave only the final version. The UEFI
`FaultTolerantWriteProtocol` makes a new copy every time a
variable is modified, leading to numerous copies in the ROM
image. For reproducibility we want only the last version.
This also will make it possible to add new variables at image
build time for things like the LinuxBoot kernel command line.