Ensure to advance cycles when waiting for interrupt to avoid stalling when mtimecmp is based on cycles.

src/main/java/li/cil/circuity/vm/riscv/R5CPU.java

@@ -199,6 +199,11 @@ public class R5CPU implements Steppable, RealTimeCounter, InterruptController {
     }
 
     public void step(final int cycles) {
+        if (waitingForInterrupt) {
+            mcycle += cycles;
+            return;
+        }
+
         final long cycleLimit = mcycle + cycles;
         while (!waitingForInterrupt && mcycle < cycleLimit) {
             final int pending = mip.get() & mie;
@@ -232,6 +237,10 @@ public class R5CPU implements Steppable, RealTimeCounter, InterruptController {
                 raiseException(e.getExceptionCause(), e.getExceptionValue());
             }
         }
+
+        if (waitingForInterrupt && mcycle < cycleLimit) {
+            mcycle = cycleLimit;
+        }
     }
 
     private void interpret() throws R5Exception, MemoryAccessException {