GF.CompileOne: use random numbers to avoid temporary file name clashes

When using make -j to compile examples/app or examples/phrasebook, since
the dependencies are not completely specified in the Makefiles, it can
happen that the same file is compiled at the same by more than one process,
resulting in an error when they try to write the same .gfo.tmp file. Adding a
random number to the temporary file name avoids this problem.

src/compiler/GF/CompileOne.hs

@@ -25,6 +25,7 @@ import GF.Data.Operations(ErrorMonad,liftErr,(+++),done)
 
 import GF.System.Directory(doesFileExist,getCurrentDirectory,renameFile)
 import System.FilePath(makeRelative)
+import System.Random(randomIO)
 import qualified Data.Map as Map
 import GF.Text.Pretty(render,(<+>),($$)) --Doc,
 import GF.System.Console(TermColors(..),getTermColors)
@@ -142,11 +143,12 @@ compileSourceModule opts cwd mb_gfFile gr =
 --writeGFO :: Options -> InitPath -> FilePath -> SourceModule -> IOE ()
 writeGFO opts cwd file mo =
     putPointE Normal opts ("  write file" +++ rfile) $
-      do encodeModule tmp mo2
+      do n <- liftIO randomIO --avoid name clashes when compiling with 'make -j'
+         let tmp = file++".tmp" ++show (n::Int)
+         encodeModule tmp mo2
          renameFile tmp file
   where
     rfile = makeRelative cwd file
-    tmp = file++".tmp"
     mo2 = (m,mi{jments=Map.filter notAnyInd (jments mi)})
     (m,mi) = subexpModule mo