Adding check for empty includes in hpvm-clang

hpvm/tools/hpvm-clang/main.py.in

@@ -237,7 +237,7 @@ def hpvm_c_to_ll(
     std: str = None,  # --std=c++11
 ) -> List[str]:
     includes = (extra_includes or []) + INCLUDE_DIRS
-    includes_s = [f"-I{path}" for path in includes]
+    includes_s = [f"-I{path}" for path in includes if path != ""]
     macros = [f"-D{macro}" for macro in (macros or [])]
     flags = [f"-f{flg}" for flg in (flags or [])]
     if std: