[OE-core] sstate.bbclass: Ensure machine specific stamps are only wiped for the current task

[Richard Purdie]

sstate was being a little too ethusiastic about removing stamp files and
was removing stamp files for other machines when it shouldn't have been.

This patch teaches sstate about machine specific stamp extensions and
allows it to only remove the current task's stampfiles.

Based on a patch from Phil Blundell <philb at gnu.org> with some tweaks
from me.

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
diff --git a/meta/classes/sstate.bbclass b/meta/classes/sstate.bbclass
index eee04ab..6abf55b 100644
--- a/meta/classes/sstate.bbclass
+++ b/meta/classes/sstate.bbclass
@@ -259,10 +259,15 @@ def sstate_clean(ss, d):
             bb.utils.unlockfile(lock)
 
     stfile = d.getVar("STAMP", True) + ".do_" + ss['task']
+    extrainf = d.getVarFlag("do_" + ss['task'], 'stamp-extra-info')
     oe.path.remove(stfile)
     oe.path.remove(stfile + "_setscene")
-    oe.path.remove(stfile + ".*")
-    oe.path.remove(stfile + "_setscene" + ".*")
+    if extrainf:
+        oe.path.remove(stfile + ".*" + extrainf)
+        oe.path.remove(stfile + "_setscene" + ".*" + extrainf)
+    else:
+        oe.path.remove(stfile + ".*")
+        oe.path.remove(stfile + "_setscene" + ".*")
 
 CLEANFUNCS += "sstate_cleanall"