feat(l0dables): Exit in case of CPU exception

Currently, misbehaving l0dables which trigger some kind of CPU exception
will busy-spin in the exception handler with no way to return to another
app without a full reboot.

Fix this by calling epic_exit() in case of an exception to hopefully
allow a return to menu in most situations.

l0dables/lib/crt.s

@@ -188,15 +188,6 @@ DefaultHandler:
 		/*
 		 * Declare all default ISRs.
 		 */
-		def_irq_handler    NMI_Handler
-		def_irq_handler    HardFault_Handler
-		def_irq_handler    MemManage_Handler
-		def_irq_handler    BusFault_Handler
-		def_irq_handler    UsageFault_Handler
-		def_irq_handler    SVC_Handler
-		def_irq_handler    DebugMon_Handler
-		def_irq_handler    PendSV_Handler
-
 		def_irq_handler    PF_IRQHandler
 		def_irq_handler    WDT0_IRQHandler
 		def_irq_handler    RTC_IRQHandler

l0dables/lib/hardware.c

@@ -128,3 +128,25 @@ uint32_t _sbrk(int incr)
 	brk += incr;
 	return (uint32_t)prev_brk;
 }
+
+void HardFault_Handler(void)
+{
+	/*
+	 * We pray that we're not currently in an API call and attempt
+	 * returning.  This is okay because a HardFault during an API call is
+	 * extremely unlikely.
+	 *
+	 * In the future, we could improve this by "finishing" an ongoing API
+	 * call before firing epic_exit().
+	 */
+	epic_exit(255);
+}
+
+/* Alias all other exception handlers to the HardFault_Handler. */
+void NMI_Handler(void) __attribute__((alias("HardFault_Handler")));
+void MemManage_Handler(void) __attribute__((alias("HardFault_Handler")));
+void BusFault_Handler(void) __attribute__((alias("HardFault_Handler")));
+void UsageFault_Handler(void) __attribute__((alias("HardFault_Handler")));
+void SVC_Handler(void) __attribute__((alias("HardFault_Handler")));
+void DebugMon_Handler(void) __attribute__((alias("HardFault_Handler")));
+void PendSV_Handler(void) __attribute__((alias("HardFault_Handler")));