os2: propogate errors from execv functions to parent

core/os/os2/process.odin

@@ -305,6 +305,7 @@ Process_Desc :: struct {
 	// A slice of strings, each having the format `KEY=VALUE` representing the
 	// full environment that the child process will receive.
 	// In case this slice is `nil`, the current process' environment is used.
+	// NOTE(laytan): maybe should be `Maybe([]string)` so you can do `nil` == current env, empty == empty/no env.
 	env: []string,
 	// The `stderr` handle to give to the child process. It can be either a file
 	// or a writeable end of a pipe. Passing `nil` will shut down the process'