libcompiler_builtins: Don't build emutls.c
libcompiler_builtins: Don't build emutls.c

Rather than improving the check, let's ditch emutls.c entirely.

aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust