[ fix ] Disable top-level constants optimisation during incremental c…

…ompilation

The optimisation for non-recursive top-level constants introduced in
 #2817 accidentally breaks incremental compilation when an optimised
top-level constant is referenced in another module (noticeable in
larger, non-trivial programs, e.g. when building Idris itself in
incremental mode).

Since incremental compilation currently has no way to know about
constants in other modules, this commit sets the list of constants to
`empty` (as is done in the `ChezSep` backend) which allows successful
compilation.

src/Compiler/Scheme/Chez.idr

@@ -658,7 +658,7 @@ incCompile c s sourceFile
                version <- coreLift $ chezVersion chez
                fgndefs <- traverse (getFgnCall version) ndefs
                (sortedDefs, constants) <- sortDefs ndefs
-               compdefs <- traverse (getScheme constants (chezExtPrim constants) chezString) sortedDefs
+               compdefs <- traverse (getScheme empty (chezExtPrim empty) chezString) sortedDefs
                let code = concat $ map snd fgndefs ++ compdefs
                Right () <- coreLift $ writeFile ssFile $ build code
                   | Left err => throw (FileErr ssFile err)