Fix MLIR build with MLIR_INCLUDE_TESTS=OFF

[nihui]

Summary

error message

/usr/bin/ld: CMakeFiles/mlir-opt.dir/mlir-opt.cpp.o: in function `main':
mlir-opt.cpp:(.text.startup.main+0xb9): undefined reference to `mlir::registerTestDialect(mlir::DialectRegistry&)'

[mehdi_amini]

Thanks!

[nihui]

I do not have commit access, someone has to commit the change for me (with attribution). Thanks

[rriddle]

In D86592#2238849, @nihui wrote:

I do not have commit access, someone has to commit the change for me (with attribution). Thanks

Please provide a Name <email> with which to attribute. (Alternatively in the future, you can use arc to upload your patch which provides attribution automatically)

[nihui]

In D86592#2238867, @rriddle wrote:

In D86592#2238849, @nihui wrote:

I do not have commit access, someone has to commit the change for me (with attribution). Thanks

Please provide a Name <email> with which to attribute. (Alternatively in the future, you can use arc to upload your patch which provides attribution automatically)

Ni Hui <[e-mail]>

Thanks !

mlir/tools/mlir-opt/mlir-opt.cpp

 #endif
   DialectRegistry registry;
   registerAllDialects(registry);
+#ifdef MLIR_INCLUDE_TESTS
   registerTestDialect(registry);
+#endif
   return failed(MlirOptMain(argc, argv, "MLIR modular optimizer driver\n",
                             registry,
                             /*preloadDialectsInContext=*/false));