replay: do not build if TCG is not available

this fixes non-TCG builds broken recently by replay reverse debugging.

Stub the needed functions in stub/, splitting roughly between functions
needed only by system emulation, by system emulation and tools,
and by everyone.  This includes duplicating some code in replay/, and
puts the logic for non-replay related events in the replay/ module (+
the stubs), so this should be revisited in the future.

Surprisingly, only _one_ qtest was affected by this, ide-test.c, which
resulted in a buzz as the bh events were never delivered, and the bh
never executed.

Many other subsystems _should_ have been affected.

This fixes the immediate issue, however a better way to group replay
functionality to TCG-only code could be developed in the long term.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20201013192123.22632-4-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

replay/stubs-system.c

@@ -0,0 +1,96 @@
+#include "qemu/osdep.h"
+#include "sysemu/replay.h"
+#include "ui/input.h"
+
+void replay_input_event(QemuConsole *src, InputEvent *evt)
+{
+    qemu_input_event_send_impl(src, evt);
+}
+
+void replay_input_sync_event(void)
+{
+    qemu_input_event_sync_impl();
+}
+
+void replay_add_blocker(Error *reason)
+{
+}
+void replay_audio_in(size_t *recorded, void *samples, size_t *wpos, size_t size)
+{
+}
+void replay_audio_out(size_t *played)
+{
+}
+void replay_breakpoint(void)
+{
+}
+bool replay_can_snapshot(void)
+{
+    return true;
+}
+void replay_configure(struct QemuOpts *opts)
+{
+}
+void replay_flush_events(void)
+{
+}
+void replay_gdb_attached(void)
+{
+}
+bool replay_running_debug(void)
+{
+    return false;
+}
+void replay_shutdown_request(ShutdownCause cause)
+{
+}
+void replay_start(void)
+{
+}
+void replay_vmstate_init(void)
+{
+}
+
+#include "monitor/monitor.h"
+#include "monitor/hmp.h"
+#include "qapi/qapi-commands-replay.h"
+#include "qapi/error.h"
+#include "qemu/error-report.h"
+
+void hmp_info_replay(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+void hmp_replay_break(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+void hmp_replay_delete_break(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+void hmp_replay_seek(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+ReplayInfo *qmp_query_replay(Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+    return NULL;
+}
+void qmp_replay_break(int64_t icount, Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+}
+void qmp_replay_delete_break(Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+}
+void qmp_replay_seek(int64_t icount, Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+}