cmake_lib.bbclass: set SSTATE_SYSROOT

SSTATE_SYSROOT is the location the recipe stages to and wher our paths
alignment usually takes place.

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>

classes/cmake_lib.bbclass

@@ -57,6 +57,8 @@
 
 inherit cmake_sysroot
 
+SSTATE_SYSROOT = "${STAGING_DIR}-components/${PACKAGE_ARCH}/${PN}"
+
 # global helper to get CMAKE_ALIGN_SYSROOT array
 def get_align_flags(d):
     ret = {}