Trying to build the build/unittests target leads to the following error

result = self.execfunction(target=target, source=rsources, env=env)
File "/usr/lib/scons/SCons/Tool/install.py", line 215, in installFunc
"Installing source %s into target %s: target and source lists must have same length."%(list(map(str, source)), list(map(str, target)))
AssertionError: Installing source ['build/opt/mongo/db/s/metadata_test', 'build/opt/mongo/rpc/metadata_test'] into target ['build/unittests/metadata_test']: target and source lists must have same length.
scons: building terminated because of errors.