Is isysroot useful for non-universal?

[Marcus Calhoun-Lopez]

It is mentioned in http://trac.macports.org/ticket/17356#comment:6
that universal builds do not suffer from bad .la files because of -isysroot.

Perhaps -isysroot could be used to solve other problems as well.
If I understand the behavior, any compiler call with
-isysroot would not see /usr/local/include.
It also does not see any changes the user might have made.

-Wl,-syslibroot,${SDK} might be used in a similar manner
(for user changes anyway).
It would still see /use/local/lib since
/Developer/SDKs/*/usr/local/lib exists and is a link to /usr/local/lib.

One big downside is that the Apple developer pages say that
support of isysroot "is likely to change in the future. "

Even still, might isysroot and syslibroot be used to cut down on bug reports?

-Marcus