oeqa/selftest/devtool: Correct git clone of local repository

If the build environment is setup using `repo`, then poky/.git/object
is a symbolic link rather than a directory. To clone such repositories,
the source path must be prefixed with "file://". This avoids the
following error:

  fatal: failed to start iterator over '.../poky/.git/objects': Not a directory

(From OE-Core rev: 8e3d08cb9274832a346ac3dffa8c9d5f6e93c478)

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/selftest/cases/devtool.py

@@ -54,7 +54,7 @@ def setUpModule():
             result = runCmd('git rev-parse --show-toplevel', cwd=canonical_layerpath)
             oldreporoot = result.output.rstrip()
             newmetapath = os.path.join(corecopydir, os.path.relpath(oldmetapath, oldreporoot))
-            runCmd('git clone %s %s' % (oldreporoot, corecopydir), cwd=templayerdir)
+            runCmd('git clone file://%s %s' % (oldreporoot, corecopydir), cwd=templayerdir)
             # Now we need to copy any modified files
             # You might ask "why not just copy the entire tree instead of
             # cloning and doing this?" - well, the problem with that is