Fix the builds with LLVM_TOOL_LLVM_DRIVER_BUILD enabled.
LLVM_ENABLE_EXPORTED_SYMBOLS_IN_EXECUTABLES is not completely
compatible with export_executable_symbols as the later will be ignored
if the previous is set to NO.
Fix the issue by passing if symbols need to be exported to
llvm_add_exectuable so the link flag can be determined directly
without calling export_executable_symbols_* later.
`LLVM_ENABLE_EXPORTED_SYMBOLS_IN_EXECUTABLES` is not completely
compatible with `export_executable_symbols` as the later will be ignored
if the previous is set to NO.
Fix the issue by passing if symbols need to be exported to
`llvm_add_exectuable` so the link flag can be determined directly
without calling `export_executable_symbols_*` later.
This reapplies 85c649bc02a, which was reverted in 35767e43d62 due to failures
with some example programs. The fix was to add export_executable_symbols to the
example programs.
Renames the llvm/examples/LLJITExamples directory to llvm/examples/OrcV2Examples
since it is becoming a home for all OrcV2 examples, not just LLJIT.
See http://llvm.org/PR31103.
