You are missing the leveldb library files:
g++: error: /home/atlas/Downloads/Slothcoin-master/src/leveldb/libleveldb.a: No such file or directory
g++: error: /home/atlas/Downloads/Slothcoin-master/src/leveldb/libmemenv.a: No such file or directory
Did you forget to compile them?
Its a missing makefile. a lot of coins have the problem