flatpack-builder make-install-args should not add install automatically

[tygerlord]

in json defining "make-install-args": [ "something" ] result in command:

make install something

If you want to make different install like defining "install-no-docs" the result become

make install install-no-docs

so you can't redefining which kind of install you want.

Maybe more convenient it's to set "install" by default if make-install-args not defined or replace completly by the new definition.

[alexlarsson]

Hmm, a more typical use of it would be to do something like make install FOO=bar, where you set FOO=bar as make-install-args, just like the make-args. But I see your point of replacing the install target.

[alexlarsson]

Maybe we could add a "install-rule": which defaults to "install".