The Library path editing dialog in Tools Options has for some time now had a button called "Delete Invalid Paths".
The first item in this library path, in Delphi XE4, due to it being a multi-platform tool, is now more complex than before, it looks like this:
However, it appears $(Platform) does not resolve within the context of this dialog box and so it appears grayed out. When users use the Delete Invalid Paths button to remove invalid paths (paths that do not exist), this will delete the most important path in the library path. No VCL application will be able to find its resource or DCU files anymore.
This is a pretty serious bug. I'm posting it here rather than on QC because it doesn't seem to me that QualityCentral gets looked at much. nevertheless, I will post it on QC eventually.
This problem frustrated several developers where I work, because the presence of extra folders in the library path sometimes confuses the compiler, and removing those malformed items (by using Delete Invalid Paths) was helpful to them, but it also kills important information that should ALWAYS be in the library path.
In my humble opinion you should just take this whole $(BDSLIB)\$(Platform)\release part OUT of the Library path in the registry permanently, and make it implicit, or else have a new $(AUTOBDSLIB) environment variable that is easy to remember and which this dialog box does not ever permit to be removed.