sstate: Avoid problems with recipes using SRCPV when fetching sstate

When fetching sstate, SRCPV can be expanded withuin PV which breaks the
sstate fetcher as other variables like SRC_URI are changed by the fetcher
code. Expand the variable before doing this to avoid those problems and
hence avoid setscene task failures with remote sstate storage in git
recipes.

(From OE-Core rev: 0d9d7acebe0be42d4cf8a30ecbbbbcb2dfd16a4b)

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

meta/classes/sstate.bbclass

@@ -731,6 +731,7 @@ def pstaging_fetch(sstatefetch, d):
     localdata.setVar('FILESPATH', dldir)
     localdata.setVar('DL_DIR', dldir)
     localdata.setVar('PREMIRRORS', mirrors)
+    localdata.setVar('SRCPV', d.getVar('SRCPV'))
 
     # if BB_NO_NETWORK is set but we also have SSTATE_MIRROR_ALLOW_NETWORK,
     # we'll want to allow network access for the current set of fetches.
@@ -755,6 +756,9 @@ def pstaging_fetch(sstatefetch, d):
         except bb.fetch2.BBFetchException:
             pass
 
+pstaging_fetch[vardepsexclude] += "SRCPV"
+
+
 def sstate_setscene(d):
     shared_state = sstate_state_fromvars(d)
     accelerate = sstate_installpkg(shared_state, d)