Document .weak usage.

khrs · khrs · commit 3047813439db · 2020-06-02T10:29:25.000+02:00
diff --git a/riscv-rt/asm.S b/riscv-rt/asm.S
@@ -125,6 +125,7 @@ _abs_start:
 */
 .section .trap, "ax"
 .global _start_trap
+/* Make it .weak so PAC/HAL can provide their own if needed. */
 .weak _start_trap
 
 _start_trap:
