Highlight that directory prefixing to control order isn't possible for some binaries

Signed-off-by: Schneems <richard.schneeman+foo@gmail.com>

Author: schneems

text/0133-explicit-layer-order.md

@@ -44,14 +44,17 @@ The "inside of the same buildpack" relies on the order of buildpack execution to
 - Today a single buildpack can write multiple layers.
 - For launch or the next buildpack in build, each layer is evaluated in alphabetic order via the spec.
 - This order can differ from the order that layers were written by the buildpack which is surprising and can result in difficult to debug problem.
-- We should introduce a mechanism that allows buildpack authors to ensure that build, launch, and "inside of the same buildpack" have the same order of environment variable modification.
+- The current ordering mechanism requires prefixing a directory to change order. Some binaries cannot be relocated without being rebuilt.
+- We should introduce a mechanism that allows buildpack authors to ensure that build, launch, and "inside of the same buildpack" have the same order of environment variable modification. This mechanism should allow non-relocatable binaries to be re-ordered.
 
 > - Why should we do this?
 
-To improve the correctness and reliability of buildpacks
+To improve the correctness and reliability of buildpacks.
 
 > - What use cases does it support?
 
+- Re-ordering layers without having to move files on disk.
+
 > - What is the expected outcome?
 
 Buildpack ordering will be more consistent for those that use this feature. The behavior will be less surprising to buildpack authors and users. Less time will be spent creatively renaming layers to achieve the desired ordering.