Harden Go-SDK build-time tooling

Follow-up comments from Ash: > Instead of Stat and ReadAT, > > you can use [Seek](https://pkg.go.dev/os#File.Seek): > f.Seek(TrailerSize, 2) > > (or maybe -TrailerSize ) > Seek sets the offset for the next Read or Write on file to offset, interpreted according to whence: 0 means relative to the origin of the file, 1 means relative to the current offset, and 2 means relative to the end. It returns the new offset and an error, if any. > > The behavior of Seek on a file opened with [O_APPEND](https://pkg.go.dev/os#O_APPEND) is not specified.pkg.go.dev[os package - os - Go Packages](https://pkg.go.dev/os#File.Seek) Package os provides a platform-independent interface to operating system functionality. > > A possible concern with appending trailing data is falling foul of virus checkers. Not sure how likely that is, but I know on Windows that sort of "trailing data" is a quite frequent sign of virus/malware etc. > I Just something to bear in mind