Pass optimization flags to rustc properly. Closes: #5788.

mesonbuild/backend/ninjabackend.py

@@ -1287,6 +1287,7 @@ int dummy;
         args += ['--crate-name', target.name]
         args += rustc.get_buildtype_args(self.get_option_for_target('buildtype', target))
         args += rustc.get_debug_args(self.get_option_for_target('debug', target))
+        args += rustc.get_optimization_args(self.get_option_for_target('optimization', target))
         args += self.build.get_global_args(rustc, target.for_machine)
         args += self.build.get_project_args(rustc, target.subproject, target.for_machine)
         depfile = os.path.join(target.subdir, target.name + '.d')

mesonbuild/compilers/rust.py

@@ -19,11 +19,11 @@ from ..mesonlib import EnvironmentException, MachineChoice, Popen_safe
 from .compilers import Compiler, rust_buildtype_args, clike_debug_args
 
 rust_optimization_args = {'0': [],
-                          'g': ['-C', '--opt-level=0'],
-                          '1': ['-C', '--opt-level=1'],
-                          '2': ['-C', '--opt-level=2'],
-                          '3': ['-C', '--opt-level=3'],
-                          's': ['-C', '--opt-level=s'],
+                          'g': ['-C', 'opt-level=0'],
+                          '1': ['-C', 'opt-level=1'],
+                          '2': ['-C', 'opt-level=2'],
+                          '3': ['-C', 'opt-level=3'],
+                          's': ['-C', 'opt-level=s'],
                           }
 
 class RustCompiler(Compiler):