sim: ppc: fallback when ln is not available [PR sim/18864]

Not all systems have easy access to hard links or symlinks, so add
fallback logic to the run->psim build code to handle those.

Bug: https://sourceware.org/PR18864

sim/arch-subdir.mk.in

@@ -26,6 +26,7 @@ EXEEXT = @EXEEXT@
 INSTALL = @INSTALL@
 INSTALL_PROGRAM = @INSTALL_PROGRAM@
 INSTALL_DATA = @INSTALL_DATA@
+LN_S = @LN_S@
 
 CC = @CC@
 C_DIALECT = @C_DIALECT@

sim/ppc/Makefile.in

@@ -522,8 +522,8 @@ psim$(EXEEXT): $(TARGETLIB) main.o $(LIBIBERTY_LIB) $(BFD_LIB) $(LIBINTL_DEP)
 	$(CC) $(CFLAGS) $(LDFLAGS) -o psim$(EXEEXT) main.o $(TARGETLIB) $(BFD_LIB) $(ZLIB) $(LIBINTL) $(LIBIBERTY_LIB) $(LIBS)
 
 run$(EXEEXT): psim$(EXEEXT)
-	rm -f run$(EXEEXT)
-	ln psim$(EXEEXT) run$(EXEEXT)
+	rm -f $@
+	ln $< $@ 2>/dev/null || $(LN_S) $< $@ 2>/dev/null || cp -p $< $@
 
 $(TARGETLIB): tmp-igen tmp-dgen tmp-hw tmp-pk tmp-defines $(LIB_OBJ) $(GDB_OBJ)
 	rm -f $(TARGETLIB)