We always want Javascript JIT to be disabled for security reasons, so when performing a MozJS upgrade we generate platform-specific files always with the --disable-jit flag, which will define JS_CODEGEN_NONE as 1, effectively disabling all possibilities of executing JIT code, since it disables the JIT backend. Here's some more examples of JIT code being disabled by the definition:

• https://github.com/10gen/mongo/blob/c61c4aba34d56b6d7feede3aba08cdedf3dda123/src/third_party/mozjs/extract/js/src/jsapi.cpp#L4262
• https://github.com/10gen/mongo/blob/master/src/third_party/mozjs/extract/js/src/jit/BaselineCodeGen.cpp#L98C1-L105C2
• https://github.com/10gen/mongo/blob/master/src/third_party/mozjs/extract/js/src/jit/Assembler.h#L28

This means that setting the disableJavaScriptJIT parameter boils down to being a no-op, so we should get rid of it. We should also clean up code that references JIT, like here, as it makes it seem like JIT is actually doing something.