This will print a set of variables from make on error using
MAKE_PRINT_VAR_ON_ERROR. It is already enabled for the DIRDEPS_BUILD.
It may make sense to enable this in the non-meta mode as well once
people are more used to its more verbose error output.
This makes it much simpler to see which .meta file is used when a
command files so that it may be inspected for the build command.
Suggested by: sjg
Approved by: re (implicit)
Sponsored by: EMC / Isilon Storage Division
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