Ensure grammar tables are generated before Rust FFI build

The Rust FFI crate compiles context_bridge.cc which includes headers
that depend on generated grammar tables (core_tables_header.inc).
Adding a dependency on spirv-tools-tables ensures these are generated
before cargo runs.

Author: LegNeato

CMakeLists.txt

@@ -410,6 +410,11 @@ endif()
 add_subdirectory(source)
 add_subdirectory(tools)
 
+# The Rust FFI build needs the grammar tables to be generated first
+if(SPIRV_ENABLE_RUST_TARGET_ENV)
+  add_dependencies(spirv-tools-ffi-rust spirv-tools-tables)
+endif()
+
 add_subdirectory(test)
 add_subdirectory(examples)