classextend.py: don't extend file for file dependency

Fix error like:
lib32-e2fsprogs-1.45.3-r0 do_package_qa: QA Issue: /usr/sbin/e2scrub_all
contained in package lib32-e2fsprogs-e2scrub requires /bin/bash,
but no providers found in RDEPENDS_lib32-e2fsprogs-e2scrub

For some lib32 packages(eg: lib32-bash, lib32-sed) which probvides files,
extend is not needed

Eg: RPROVIDES of lib32-bash expects to have /bin/bash, with original
extend, it will become lib32-/bin/bash, then will cause above error

Fix by don't extend file dependency, and skip multilib check for file dependency
in do_package_qa to avoid error like:
WARNING: lib32-bash-5.0-r0 do_package: QA Issue: lib32-bash package lib32-bash
 - suspicious values '/bin/bash /bin/sh' in RPROVIDES [multilib]

(From OE-Core rev: a9163120ed52534e7dbf4db50dc2b03bbf69f06b)

Signed-off-by: Changqing Li <changqing.li@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/classextend.py

@@ -24,6 +24,8 @@ class ClassExtender(object):
             if not subs.startswith(self.extname):
                 return "virtual/" + self.extname + "-" + subs
             return name
+        if name.startswith("/"):
+            return name
         if not name.startswith(self.extname):
             return self.extname + "-" + name
         return name