Couple of fixes to LLVM AOT compiler on Windows x64. (#13474)
* Enable MSVC objects on LLVM >= 6.00
* Always used PIC relocation-model on Windows x64 due to LLVM problem with
static triggering incorrect ADDR32 relocation entries in 64-bit objects.
* Add CodeView symbol format instead of DWARF for Windows x64.
* Fix LLVM outfile when doing static link to not end up in temp directory.
* Only add /DEFAULTLIB when using MSVC and not doing static compile. For
static compile the needed libraries must be added when objects get's linked
and since the needed libraries are c-runtime libraries, should be transparent
for most applications consuming the object files.