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.

kgnk/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide