Merge bitcoin#11443: [qa] Allow "make cov" out-of-tree; Fix rpc mappi…

…ng check

fae60e3 qa: Fix lcov for out-of-tree builds (MarcoFalke)
fae2673 qa: check-rpc-mapping must not run on empty lists (MarcoFalke)

Pull request description:

  Random qa fixups:

  * `make cov` should work for out-of-tree builds
  * `check-rpc-mappings.py` should assert that it is actually checking something and the lists are not empty.

Tree-SHA512: 2b66f69d6a1ae035c772f8ceb1d58dce904d98058330dad6ccb1421941e167aa748fe1c12126b87f43b0843f51fa85d89de079d586629fcaf8261c44a8dc6053

contrib/devtools/check-rpc-mappings.py

@@ -68,7 +68,7 @@ def process_commands(fname):
                     else:
                         args = []
                     cmds.append(RPCCommand(name, args))
-    assert not in_rpcs, "Something went wrong with parsing the C++ file: update the regexps"
+    assert not in_rpcs and cmds, "Something went wrong with parsing the C++ file: update the regexps"
     return cmds
 
 def process_mapping(fname):
@@ -91,7 +91,7 @@ def process_mapping(fname):
                     idx = int(m.group(2))
                     argname = parse_string(m.group(3))
                     cmds.append((name, idx, argname))
-    assert not in_rpcs
+    assert not in_rpcs and cmds
     return cmds
 
 def main():