Correctly copy symlinks to the dpctl dir. (#455)

* Correctly copy symlinks to the dpctl dir, but avoid copying if the symlink was previously copied.

Author: Diptorup Deb

scripts/build_backend.py

@@ -143,7 +143,16 @@ def build_backend(
         for file in glob.glob(
             os.path.join(dpctl_dir, "install", "lib", "*.so*")
         ):
-            shutil.copy(file, os.path.join(dpctl_dir, "dpctl"))
+            # Check if the file already exists before copying. The check is
+            # needed when dealing with symlinks.
+            if not os.path.exists(
+                os.path.join(dpctl_dir, "dpctl", os.path.basename(file))
+            ):
+                shutil.copy(
+                    src=file,
+                    dst=os.path.join(dpctl_dir, "dpctl"),
+                    follow_symlinks=False,
+                )
     elif IS_WIN:
         if os.path.exists(os.path.join(DPCPP_ROOT, "bin", "dpcpp.exe")):
             cmake_compiler_args = [