You need the "Geth & Tools 1.7.0" package from the official Downloads page. You should be able to just unzip the package and run the binaries directly.
However, it should be noted that the
disasm tool no longer exists by itself - it was integrated with the main
evm tool in commit #3729. Meaning you'll have to run the
evm tool and pass the
disasm flag as an argument.
The other option is to compile the tool yourself using the
disasm.go file, and whatever other Go packages are required. This is the approach used in the previous answer you've linked to, but you'll need to understand how to pull everything together for the compilation. The main file has changed locations to the following: