src.sys.obj.mk export OBJTOP

[sjg]

Summary

It is necessary to export OBJTOP when it is being used
by MAKEOBJDIR, otherwise we get invalid expansions which
lead to attempts to use directories like /bin /etc /lib as .OBJDIR

Since OBJTOP may have variables like ${MACHINE} we need to export
it in such a manner that these will be correctly evaluated, so
like MAKEOBJDIR double the $'s and use .export-env OBJTOP before
evaluating it for use.

[sjg]

Remove all but the last := for OBJTOP

[jrtc27]

Do we need to worry about $s in OBJROOT?

[jrtc27]

share/mk/src.sys.obj.mk

95

Is there a risk this will propagate to sub makes where one of the other branches should be taken?

[sjg]

In D54819#1253097, @jrtc27 wrote:

Do we need to worry about $s in OBJROOT?

To the extent I grok the intent of this arrangement, I don't think so. When they are going to add $${MACHINE} etc to OBJTOP they use ${OBJROOT:H} to remove $${TARGET} etc from exported OBJROOT.

share/mk/src.sys.obj.mk

95

That will certainly happen - can't work otherwise, but whether that is a "risk" I don't know.

FWIW my normal builds set *all* this stuff in env before running make, and have never seen a problem, but I only use buildworld and only to check I didn't break it.

I could only reproduce these issues by running make with none of this stuff in env to begin with.