Makefile - Make it a bit more usable

[omesser]

• Adding target to build leo and terraform-provider-iterative binaries in repo root
• build target now uses the above instead of the current "check-build" (checks validity, but produces no binaries, which might be useful)
• install_tpi target - built and installed leo bin into tf plugins (probably unwanted behavior) - fixed
• Added phony directives for phony targets (which also allows for the convenience of make targets which acts as --help)
• Some light refactoring
• Addition to gitignore for JB ideas

[omesser]

Why does the leo binary have a GO{OS,ARCH} suffix? 🤔 I'd assume that local developers won't do that much cross-compilation.

@0x2b3bfa0 Just a good practice IMO to make those explicit - always set up things with cross-compilation in mind, at some point someone will test different GOOS/GOARCH and binaries will override and it will be annoying, and no real downsides (it's a suffix, tab-completion removes terminal-unweildliness).

So - just personal preference / practice. If you (or anyone) find this detrimental I'll just remove 😄

[0x2b3bfa0]

[...] at some point someone will test different GOOS/GOARCH [..] If you (or anyone) find this detrimental I'll just remove

This is too subjective to unbury my “detrimental sledgehammer” but I can't imagine any plausible case where cross-compiling this project during local development would become a commonplace practice. 🤷🏼‍♂️