[syslinux] EFI build problems

[Gene Cumm]

Ferenc, I have a better solution for now but I have some questions for
Matt regarding why this is the way it is.

Matt, after all of this I have some questions about why this was done
the way it is.

1) Why use shell scripts to isolate rather than just clearing
MAKEFLAGS in the Makefile
(https://www.gnu.org/software/make/manual/html_node/Options_002fRecursion.html)?

2) When parallelizing the build, it may attempt to build gnu-efi for
ia32 and x86-64 at about the same time.  This looks like we need at
least a pseudo-lock to stall one job while the other completes.

-- 
-Gene