[ORC-RT] Invert the layout of the trivial-jit-re-dlopen testcase.

Compiles and moves the original C code for main to Inputs/dlopen-dlclose-x2.S,
where it can be shared with other testcases that want a
dlopen-dlclose-dlopen-dlclose sequence. The assembly containging the
initializers to be tested is moved into the test file.