compiler: introduce QEMU_ANNOTATE

Allow a more shorter syntax when defining wrapper macros for
__attribute__((annotate(...))).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/compiler.h

@@ -197,4 +197,10 @@
 #define BUILTIN_SUBCLL_BROKEN
 #endif
 
+#if __has_attribute(annotate)
+#define QEMU_ANNOTATE(x) __attribute__((annotate(x)))
+#else
+#define QEMU_ANNOTATE(x)
+#endif
+
 #endif /* COMPILER_H */

include/qemu/osdep.h

@@ -185,7 +185,7 @@ extern "C" {
  *   }
  */
 #ifdef __clang__
-#define coroutine_fn __attribute__((__annotate__("coroutine_fn")))
+#define coroutine_fn QEMU_ANNOTATE("coroutine_fn")
 #else
 #define coroutine_fn
 #endif
@@ -195,7 +195,7 @@ extern "C" {
  * but can handle running in non-coroutine context too.
  */
 #ifdef __clang__
-#define coroutine_mixed_fn __attribute__((__annotate__("coroutine_mixed_fn")))
+#define coroutine_mixed_fn QEMU_ANNOTATE("coroutine_mixed_fn")
 #else
 #define coroutine_mixed_fn
 #endif
@@ -224,7 +224,7 @@ extern "C" {
  *   }
  */
 #ifdef __clang__
-#define no_coroutine_fn __attribute__((__annotate__("no_coroutine_fn")))
+#define no_coroutine_fn QEMU_ANNOTATE("no_coroutine_fn")
 #else
 #define no_coroutine_fn
 #endif