meson: generate trace events for qmp commands

1. Use --gen-trace when generate qmp commands
2. Add corresponding .trace-events files as outputs in qapi_files
   custom target
3. Define global qapi_trace_events list of .trace-events file targets,
   to fill in trace/qapi.build and to use in trace/meson.build
4. In trace/meson.build use the new array as an additional source of
   .trace_events files to be processed

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20220126161130.3240892-5-vsementsov@virtuozzo.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/qapi/meson.build b/qapi/meson.build
index c0c49c1..b22558c 100644
--- a/qapi/meson.build
+++ b/qapi/meson.build
@@ -114,6 +114,7 @@
       'qapi-events-@0@.h'.format(module),
       'qapi-commands-@0@.c'.format(module),
       'qapi-commands-@0@.h'.format(module),
+      'qapi-commands-@0@.trace-events'.format(module),
     ]
   endif
   if module.endswith('-target')
@@ -126,7 +127,7 @@
 qapi_files = custom_target('shared QAPI source files',
   output: qapi_util_outputs + qapi_specific_outputs + qapi_nonmodule_outputs,
   input: [ files('qapi-schema.json') ],
-  command: [ qapi_gen, '-o', 'qapi', '-b', '@INPUT0@' ],
+  command: [ qapi_gen, '-o', 'qapi', '-b', '@INPUT0@', '--gen-trace' ],
   depend_files: [ qapi_inputs, qapi_gen_depends ])
 
 # Now go through all the outputs and add them to the right sourceset.
@@ -137,6 +138,9 @@
   if output.endswith('.h')
     genh += qapi_files[i]
   endif
+  if output.endswith('.trace-events')
+    qapi_trace_events += qapi_files[i]
+  endif
   util_ss.add(qapi_files[i])
   i = i + 1
 endforeach
@@ -145,6 +149,9 @@
   if output.endswith('.h')
     genh += qapi_files[i]
   endif
+  if output.endswith('.trace-events')
+    qapi_trace_events += qapi_files[i]
+  endif
   specific_ss.add(when: 'CONFIG_SOFTMMU', if_true: qapi_files[i])
   i = i + 1
 endforeach