toolchain-script.bbclass: Collected cached site config in runtime.

[YOCTO #892]
Modify the function toolchain_create_sdk_siteconfig to collect the
cached site config files which are specified by
TOOLCHAIN_NEED_CONFIGSITE_CACHE in runtime.

Also added task dependency to ensure the cached site config files are
generated.

(From OE-Core rev: 9e87f1347788beed181476dc4563085db14a4729)

Signed-off-by: Lianhao Lu <lianhao.lu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/siteinfo.bbclass

@@ -118,7 +118,7 @@ python () {
         bb.fatal("Please add your architecture to siteinfo.bbclass")
 }
 
-def siteinfo_get_files(d):
+def siteinfo_get_files(d, no_cache = False):
     sitedata = siteinfo_data(d)
     sitefiles = ""
     for path in d.getVar("BBPATH", True).split(":"):
@@ -127,6 +127,8 @@ def siteinfo_get_files(d):
             if os.path.exists(filename):
                 sitefiles += filename + " "
 
+    if no_cache: return sitefiles
+
     # Now check for siteconfig cache files
     path_siteconfig = bb.data.getVar('SITECONFIG_SYSROOTCACHE', d, 1)
     if os.path.isdir(path_siteconfig):