Fix (p)install of compile_et (addendum)

Fix (p)install of compile_et (addendum)

A prior update (ChangeID: Ie6af2d3fd9c5166dd2d884c22d287c180b24fab1)
stops compile_et from being (p)installed into a separate directory.
Unfortunately, there's a second rule in the Makefile exhibiting the
same behaviour that was missed (the decision of which rule is used is
determined by whether a 'make install' or 'make dest' is requested).
This patch fixes the second ruleset as well.

Change-Id: I0e94d5cf0bb4e46a24fba6e77aa6baff2118f78b
Reviewed-on: http://gerrit.openafs.org/1397
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>