sim-se: Correctly calculate next PC in clone

The clone syscall doesn't propagate all state in the PCState object
when calculating the return PC of a newly created process. Instead of
creating a new PCState object from the next PC address, copy the old
PC and advance it.

Change-Id: Ice53831920bcb5d198865169ed2cca8d06e37cfe
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Cc: Giacomo Travaglini <giacomo.travaglini@arm.com>
Cc: Javier Setoain <javier.setoain@arm.com>
Cc: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15417
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Brandon Potter <Brandon.Potter@amd.com>

src/sim/syscall_emul.hh

@@ -1402,7 +1402,9 @@ cloneFunc(SyscallDesc *desc, int callnum, Process *p, ThreadContext *tc)
     ctc->setIntReg(TheISA::SyscallPseudoReturnReg, 1);
 #endif
 
-    ctc->pcState(tc->nextInstAddr());
+    TheISA::PCState cpc = tc->pcState();
+    cpc.advance();
+    ctc->pcState(cpc);
     ctc->activate();
 
     return cp->pid();