--feature is an option for cargo but not for rustc.

Reported-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Bernhard Beschow <shentey@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/qemu-api/meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index ccb20f38c1d..9425ba7100c 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -7,7 +7,7 @@ if rustc.version().version_compare('>=1.77.0')
   _qemu_api_cfg += ['--cfg', 'has_offset_of']
 endif
 if get_option('debug_mutex')
-  _qemu_api_cfg += ['--feature', 'debug_cell']
+  _qemu_api_cfg += ['--cfg', 'feature="debug_cell"']
 endif
 
 _qemu_api_rs = static_library(
-- 
2.47.1