bitbake.conf: We only care about the absolute value of baselib

The value of baselib can be constructed in several different ways and from a sstate perspective we don't care how it was made up, we only care what the final value is. This uses the new functionality in bitbake to ensure we only include the value of baselib and not any intermediate dependencies.

[YOCTO #1583]

---

index 01f064c..43d973d 100644
@@ -8,6 +8,7 @@
 
 # Used by multilib code to change the library paths
 baselib = "${BASELIB}"
+baselib[vardepvalue] = "${baselib}"
 BASELIB = "lib"
 BASELIB_powerpc64 = "lib64"