Whisk together lime juice, garlic, red-pepper flakes, and 1/4 tsp. salt, then add oil in a slow stream, whisking well. Whisk in cilantro. Pat pork dry and season with salt and pepper. Grill pork chops, covered, turning over once, until just cooked through, 5 to 6 minutes total. Serve drizzled with some vinaigrette, and with remainder on the side.