On a relatively fresh Linux this should do:
cd mkcl ./configure make
MKCL requires the platform supplied GMP library (>= 4.3.2), and GMP development files when compiling MKCL from its sources.
On Debian based systems you can install it using:
sudo apt-get install libgmp-dev
You can “install” MKCL locally into the source directory by:
cd mkcl/src make install-local
Once it’s done you can use the ./mkcl/src/bin/mkcl executable to start MKCL, either directly or through a symlink. You may want to use ‘rlwrap mkcl’ to enable line editing.
If you so prefer then you can install MKCL using ‘make install’ under the filesystem prefix given to the configure script (it defaults to ‘/usr/local’).