This obsoletes the _SKIP_BUILD check but keeps it for now until it
proves to be enough.
In the dirdeps build the first 'make all' or 'make' ran would invoke
'make dirdeps' which builds dependencies and then builds the current
directory in a sub-make (when BUILD_AT_LEVEL0 is no, which for us it
is). This behavior causes things attached to 'all:' to build in the
dirdeps phase AND the sub-make phase which creates all kinds of problems
for staging, meta file tracking, and races.
Sponsored by: EMC / Isilon Storage Division
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