bitbake: data_smart: Fix multiple override interaction with append and prepend operators

Variables which used multiple overrides and the append/prepend operators were
not functioning correctly. This change fixes that.

This fixes the testcase:

OVERRIDES = "linux:x86"
TESTVAR = "original"
TESTVAR_append_x86 = " x86"
TESTVAR_append_x86_linux = " x86+linux"
TESTVAR_append_linux_x86 = " linux+x86"

[YOCTO #2672]

(Bitbake rev: dc35a2e506e15fb7ddbf74c3b3280e9e83ab33bb)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -198,7 +198,12 @@ class DataSmart(MutableMapping):
                 for append in appends:
                     keep = []
                     for (a, o) in self.getVarFlag(append, op) or []:
-                        if o and not o in overrides:
+                        match = True
+                        if o:
+                            for o2 in o.split("_"):
+                                if not o2 in overrides:
+                                    match = False
+                        if not match:
                             keep.append((a ,o))
                             continue