fix(scripts/develop): skip build on Windows via build tag (#23118)

Previously main.go used syscall.SysProcAttr{Setpgid: true} and
syscall.Kill, both undefined on Windows. This broke GOOS=windows
cross-compilation.

Add a //go:build !windows constraint to the package since it is
a dev-only tool that requires Unix utilities (bash, make, etc.)
and is not intended to run on Windows.

Refs #23054
Fixes coder/internal#1407

scripts/develop/main.go

@@ -1,3 +1,5 @@
+//go:build !windows
+
 // Command develop orchestrates the Coder development environment. It
 // builds the binary, starts the API server and frontend dev server,
 // sets up a first user, and handles graceful shutdown on signals.

scripts/develop/main_test.go

@@ -1,3 +1,5 @@
+//go:build !windows
+
 package main
 
 import (