refactor: Add install script for coder CLI (#243)

This adds a `make install` target that copies the CLI and other coder binaries to `$GOPATH/bin` Intended to be helpful for developers who aren't familiar with `go` or the directory structure, in running `coder` CLI locally.

Makefile

@@ -1,3 +1,5 @@
+INSTALL_DIR=$(shell go env GOPATH)/bin
+
 bin/coder:
 	mkdir -p bin
 	go build -o bin/coder cmd/coder/main.go
@@ -51,6 +53,12 @@ fmt: fmt/prettier fmt/sql
 gen: database/generate peerbroker/proto provisionersdk/proto provisionerd/proto
 .PHONY: gen
 
+install: 
+	@echo "--- Copying from bin to $(INSTALL_DIR)"
+	cp -r ./bin $(INSTALL_DIR)
+	@echo "-- CLI available at $(shell ls $(INSTALL_DIR)/coder*)"
+.PHONY: install
+
 peerbroker/proto: peerbroker/proto/peerbroker.proto
 	protoc \
 		--go_out=. \