[python][amd] Check backend path for libamdhip64.so (#6598)

At Meta, we want to distribute libamdhip64.so alongside the AMD backend,
similar to how we already distribute ptxas and ld.lld.

Author: danzimm

third_party/amd/backend/driver.py

@@ -81,6 +81,12 @@ def _get_path_to_hip_runtime_dylib():
 
     paths = []
 
+    # Check backend
+    local_lib = os.path.join(os.path.dirname(__file__), "lib", lib_name)
+    if os.path.exists(local_lib):
+        return local_lib
+    paths.append(local_lib)
+
     import site
     # First search the HIP runtime dynamic library packaged with PyTorch. It's very likely
     # that we run Triton together with PyTorch. This makes sure we use the same dynamic