Remove the use of addEarlyAsPossible while setting up the pass structure in CodeGen_LLVM.
Remove the use of addEarlyAsPossible while setting up the pass
structure in CodeGen_LLVM.

This is done because addEarlyAsPossible on LLVM_VERSION >= 39 is
not functionally equivalent to calling adjustPassManager when
LLVM_VERSION >= 50.


Former-commit-id: f844f9acc2e58d3fe6ef2b73719e7362a3fa7bd4
darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide