Bug 1753402 - Disable untagged union in Gecko profiler bindings. r=canaltinova

We don't use unions in the bindings, and rust is very picky with what
you can put on untagged unions, so disable them for now.

Differential Revision: https://phabricator.services.mozilla.com/D137837

tools/profiler/rust-api/build.rs

@@ -61,6 +61,7 @@ fn generate_bindings() {
     let mut builder = Builder::default()
         .enable_cxx_namespaces()
         .with_codegen_config(CodegenConfig::TYPES | CodegenConfig::VARS | CodegenConfig::FUNCTIONS)
+        .disable_untagged_union()
         .size_t_is_usize(true);
 
     for dir in SEARCH_PATHS.iter() {