[OE-core] [PATCH] sstate: Exclude SSTATE_EXTRAPATH from checksums

[Richard Purdie]

After the change to allow target recipes to depend on native recipes, the
native checksums becomes all the more critical. Add to this that we're now
accounting for pre/postfuncs and we have a cache reuse issue since the
distro LSB string is getting coded in when it shouldn't be.

This excludes that string and allows one set of native sstate to share
checksums with another set from a different host distro. They're separated
into different directories so this is fine for our use cases.

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
diff --git a/meta/classes/sstate.bbclass b/meta/classes/sstate.bbclass
index ec9c546..f7bd117 100644
--- a/meta/classes/sstate.bbclass
+++ b/meta/classes/sstate.bbclass
@@ -17,6 +17,10 @@ SSTATE_EXTRAPATH   = ""
 SSTATE_EXTRAPATHWILDCARD = ""
 SSTATE_PATHSPEC   = "${SSTATE_DIR}/${SSTATE_EXTRAPATHWILDCARD}*/${SSTATE_PKGSPEC}"
 
+# We don't want the sstate to depend on things like the distro string
+# of the system, we let the sstate paths take care of this.
+SSTATE_EXTRAPATH[vardepvalue] = ""
+
 SSTATE_DUPWHITELIST = "${DEPLOY_DIR_IMAGE}/ ${DEPLOY_DIR}/licenses/"
 # Also need to make cross recipes append to ${PN} and install once for any given PACAGE_ARCH so
 # can avoid multiple installs (e.g. routerstationpro+qemumips both using mips32)