builder: sizes: list interrupt vector as a pseudo-package for -size=full

This is another bit of memory that is now correctly accounted for in
`-size=full`.

tools/gen-device-svd/gen-device-svd.go

@@ -1422,6 +1422,9 @@ __isr_vector:
 	for _, intr := range device.Interrupts {
 		fmt.Fprintf(w, "    IRQ %s_IRQHandler\n", intr.Name)
 	}
+	w.WriteString(`
+.size __isr_vector, .-__isr_vector
+`)
 	return w.Flush()
 }