tasks/task-poky: make the file manager a conditional part of the task

mips doesn't support pcmanfm so make it a conditional part of the task by
creating a variable, FILEMANAGER, set to pcmanfm by default and empty for mips

Signed-off-by: Joshua Lock <josh@linux.intel.com>

meta/packages/tasks/task-poky.bb

@@ -28,6 +28,10 @@ ALLOW_EMPTY = "1"
 
 SPLASH ?= "psplash"
 
+# pcmanfm doesn't work on mips
+FILEMANAGER ?= "pcmanfm"
+FILEMANAGER_mips ?= ""
+
 RDEPENDS_task-poky-apps-console = "\
     avahi-daemon \
     dropbear \
@@ -58,7 +62,7 @@ RDEPENDS_task-poky-x11-base = "\
 
 RDEPENDS_task-poky-apps-x11-core = "\
     leafpad \
-    pcmanfm \
+    ${FILEMANAGER} \
     matchbox-terminal \
     screenshot"