[PATCH] meson: Don't make object files for dtrace on macOS

[Roman Bolshakov]

dtrace on macOS uses unresolved symbols with a special prefix to define
probes [1], only headers should be generated for USDT (dtrace(1)). But
it doesn't support backwards compatible no-op -G flag [2] and implicit
build rules fail.

1. https://markmail.org/message/6grq2ygr5nwdwsnb
2. https://markmail.org/message/5xrxt2w5m42nojkz

Cc: Daniel P. Berrangé <berrange@redhat.com>
Cc: Cameron Esfahani <dirty@apple.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 trace/meson.build | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

This is an update of the previous patch that is no longer valid due to
conversion of the build system to meson:
https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg02493.html

diff --git a/trace/meson.build b/trace/meson.build
index 56e870848e..1c1fb31a61 100644
--- a/trace/meson.build
+++ b/trace/meson.build
@@ -39,12 +39,15 @@ foreach dir : [ '.' ] + trace_events_subdirs
                                    output: fmt.format('trace-dtrace', 'h'),
                                    input: trace_dtrace,
                                    command: [ 'dtrace', '-o', '@OUTPUT@', 
'-h', '-s', '@INPUT@' ])
-    trace_dtrace_o = custom_target(fmt.format('trace-dtrace', 'o'),
-                                   output: fmt.format('trace-dtrace', 'o'),
-                                   input: trace_dtrace,
-                                   command: [ 'dtrace', '-o', '@OUTPUT@', 
'-G', '-s', '@INPUT@' ])
+    trace_ss.add(trace_dtrace_h)
+    if host_machine.system() != 'darwin'
+      trace_dtrace_o = custom_target(fmt.format('trace-dtrace', 'o'),
+                                     output: fmt.format('trace-dtrace', 'o'),
+                                     input: trace_dtrace,
+                                     command: [ 'dtrace', '-o', '@OUTPUT@', 
'-G', '-s', '@INPUT@' ])
+      trace_ss.add(trace_dtrace_o)
+    endif
 
-    trace_ss.add(trace_dtrace_h, trace_dtrace_o)
     genh += trace_dtrace_h
   endif
 endforeach
-- 
2.24.3 (Apple Git-128)