scripts/yocto-check-layer: Don't abort when layer fails to get signatures

When execute in multiple layers like meta-openembedded the execution is
aborted when some sublayer fails to get world signatures, so mark it as
an error and continue the execution in the remaining sublayers.

(From OE-Core rev: c8ab558b4fdc77ab54fbb130078c78d43740b4b8)

Signed-off-by: Aníbal Limón <anibal.limon@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/yocto-check-layer

@@ -169,7 +169,14 @@ def main():
         td['bbvars'] = get_bb_vars()
         logger.info('Getting initial signatures ...')
         td['builddir'] = builddir
-        td['sigs'], td['tunetasks'] = get_signatures(td['builddir'])
+        try:
+            td['sigs'], td['tunetasks'] = get_signatures(td['builddir'])
+        except RuntimeError as e:
+            logger.info(str(e))
+            results[layer['name']] = None
+            results_status[layer['name']] = 'FAIL (Generating world signatures)'
+            layers_tested = layers_tested + 1
+            continue
         td['machines'] = args.machines
 
         if not add_layer(bblayersconf, layer, dep_layers, logger):