MFC r266416:
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    r266416 | bjk | 2014-05-18 17:05:54 -0400 (Sun, 18 May 2014) | 14 lines

    Document some user-settable make variables in ports.7

    This is not a comprehensive list, as the variables themselves are spread
    out over multiple files, but it is a start.

    Add a section to make.conf noting that variables may be set there that
    affect ports builds, but refer to ports.7 and elsewhere for the actual
    listing; any listing in make.conf.5 would likely become out of date
    fairly quickly.

    PR:             docs/189199
    Reviewed by:    bdrewery (previous version)
    Approved by:    hrs (mentor)

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PR:		189199
Approved by:	re (gjb), hrs (mentor)