sstate: Allow late expansion of NATIVELSBSTRING

uninative needs to adjust NATIVELSBSTRING fairly late in the
configuration parsing process but the sstate code encodes it into
variables. Since this string doesn't vary on a per recipe basis, we
defer its expansion until usage time.

(From OE-Core rev: fb680ab8b3cf7aba9b579403b1aeb96d30762320)

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

meta/classes/sstate.bbclass

@@ -31,7 +31,7 @@ SSTATE_DUPWHITELIST += "${DEPLOY_DIR_SRC}"
 SSTATE_SCAN_FILES ?= "*.la *-config *_config"
 SSTATE_SCAN_CMD ?= 'find ${SSTATE_BUILDDIR} \( -name "${@"\" -o -name \"".join(d.getVar("SSTATE_SCAN_FILES", True).split())}" \) -type f'
 
-BB_HASHFILENAME = "${SSTATE_EXTRAPATH} ${SSTATE_PKGSPEC} ${SSTATE_SWSPEC}"
+BB_HASHFILENAME = "False ${SSTATE_PKGSPEC} ${SSTATE_SWSPEC}"
 
 SSTATE_ARCHS = " \
     ${BUILD_ARCH} \
@@ -79,6 +79,7 @@ python () {
 
     if bb.data.inherits_class('native', d) or bb.data.inherits_class('crosssdk', d) or bb.data.inherits_class('cross', d):
         d.setVar('SSTATE_EXTRAPATH', "${NATIVELSBSTRING}/")
+        d.setVar('BB_HASHFILENAME', "True ${SSTATE_PKGSPEC} ${SSTATE_SWSPEC}")
         d.setVar('SSTATE_EXTRAPATHWILDCARD', "*/")
 
     # These classes encode staging paths into their scripts data so can only be
@@ -721,7 +722,10 @@ def sstate_checkhashes(sq_fn, sq_task, sq_hash, sq_hashfn, d, siginfo=False):
         # Magic data from BB_HASHFILENAME
         splithashfn = sq_hashfn[task].split(" ")
         spec = splithashfn[1]
-        extrapath = splithashfn[0]
+        if splithashfn[0] == "True":
+            extrapath = d.getVar("NATIVELSBSTRING", True) + "/"
+        else:
+            extrapath = ""
 
         tname = sq_task[task][3:]