We might have more uses for --cfg MESON, even though right now it's only
qemu-api that has generated files.  Since we're going to add more flags
to the add_project_arguments calls for Rust, it makes sense to also add
--cfg MESON everywhere.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 meson.build               | 7 ++++---
 rust/qemu-api/meson.build | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/meson.build b/meson.build
index e0b880e4e13..a6172524287 100644
--- a/meson.build
+++ b/meson.build
@@ -3422,10 +3422,11 @@ if have_rust
   # is safe; https://github.com/rust-lang/rust/pull/54675 says that
   # passing -nodefaultlibs to the linker "was more ideological to
   # start with than anything".
-  add_project_arguments(rustc_args + ['-C', 'default-linker-libraries'],
+  add_project_arguments(rustc_args +
+      ['--cfg', 'MESON', '-C', 'default-linker-libraries'],
       native: false, language: 'rust')
-
-  add_project_arguments(rustc_args, native: true, language: 'rust')
+  add_project_arguments(rustc_args + ['--cfg', 'MESON'],
+      native: true, language: 'rust')
 endif
 
 hxtool = find_program('scripts/hxtool')
diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index 6f637af7b1b..cad9ac4844e 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -1,4 +1,4 @@
-_qemu_api_cfg = ['--cfg', 'MESON']
+_qemu_api_cfg = []
 # _qemu_api_cfg += ['--cfg', 'feature="allocator"']
 if rustc.version().version_compare('>=1.77.0')
   _qemu_api_cfg += ['--cfg', 'has_offset_of']
-- 
2.47.0