Clear up guile2 vs. guile cmake confusion

CMakeLists.txt

@@ -261,7 +261,7 @@ IF (GUILE2_FOUND) # found guile-2.0
   SET(GUILE_INCLUDE_DIRS ${GUILE2_INCLUDE_DIRS})
   SET(GUILE_LDFLAGS ${GUILE2_LDFLAGS})
 
-  FIND_PROGRAM (GUILD_EXECUTABLE guild)
+  FIND_PROGRAM (GUILD_EXECUTABLE guild2.0 guild)
   IF (NOT GUILD_EXECUTABLE)
     MESSAGE (SEND_ERROR "The guild executable was not found, but is required. Please set GUILD_EXECUTABLE.")
   ENDIF (NOT GUILD_EXECUTABLE)
@@ -280,7 +280,7 @@ ELSE()
   MESSAGE(STATUS "Using guile-1.8.x")
 ENDIF()
 
-FIND_PROGRAM (GUILE_EXECUTABLE guile)
+FIND_PROGRAM (GUILE_EXECUTABLE guile2.0 guile)
 IF (NOT GUILE_EXECUTABLE)
   MESSAGE (SEND_ERROR "The guile executable was not found, but is required. Please set GUILE_EXECUTABLE.")
 ENDIF (NOT GUILE_EXECUTABLE)