fix(rocm): prefer system LLVM runtime on native Linux (#7448)

* fix(rocm): prefer system LLVM runtime on native Linux

* Fix/adjust the nested LLVM probe for PR #7448: lib64 hosts and non-directories

Two gaps found while simulating the fix against real ROCm layouts.

1. lib64 hosts got no LLVM dir. The candidate was built from the HSA dir, so a
   host with libhsa-runtime64 under lib64 probed <root>/lib64/llvm/lib. ROCm
   installs LLVM under <root>/lib/llvm regardless, so that host kept binding
   system libamd_comgr to the bundle's libLLVM: exactly the bug #7446 reports.
   Probe both spellings, the HSA dir's own first so a genuine lib64 layout still
   wins. When lib_sub is already "lib" the seen set collapses them.

2. os.path.exists accepted a non-directory. The serve-time caller joins these
   straight into LD_LIBRARY_PATH with no is-dir filter, so a file named
   llvm/lib reached the loader. os.path.isdir instead.

Verified on a 27-case matrix built from real directory trees (not mocks), run on
both Windows and Linux against three revisions: main, this PR as-is, and this
commit. Zero regressions and zero reorderings of the pre-existing entries in
every case, and the installer and launcher copies never disagree. The lib64 case
goes [lib64] -> [lib64, lib/llvm/lib]; the file case drops the bogus entry; a
symlinked llvm/lib resolves correctly on Linux.

End-to-end loader check: built real ELF objects mirroring the shipped bundle
(RUNPATH=$ORIGIN, an incomplete libLLVM.so.23.0git next to llama-server, system
comgr from /opt/rocm/lib) and reproduced the reported failure verbatim, then
confirmed the prepend clears it:
  before  undefined symbol: LLVMInitializeSPIRVTarget  ->  after  exit 0

Test helper now patches os.path.isdir alongside os.path.exists, else every fake
host reports its nested llvm dir as missing. New cases: lib64 finding llvm under
lib, lib64 preferring its own when both exist, and a real-filesystem check that a
non-directory is not prepended. Removing the lib fallback from one copy reddens
three tests including the two-copy parity guard.

tests/studio/install: 1361 passed on Linux, 4 pre-existing environmental
failures unchanged (3 managed-node-runtime under root, 1 the real /opt/rocm case
already covered by #7397). 30/30 on the helper suite on Windows and Linux.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Daniel Han <danielhanchen@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/studio/install/test_rocm_native_linux_lib_dirs.py

@@ -124,7 +124,12 @@ def _call(
     tmp_path factory branches on it, so a session-wide patch breaks the fixture on
     a Windows test host."""
     with patch.object(sys, "platform", platform):
-        with patch("os.path.exists", _fake_exists(present)):
+        # isdir too: the llvm probe requires a directory, so a fake host that only
+        # answers exists() would report every nested llvm dir as missing.
+        with (
+            patch("os.path.exists", _fake_exists(present)),
+            patch("os.path.isdir", _fake_exists(present)),
+        ):
             return _norm(impl(str(bundle)))
 
 
@@ -260,6 +265,78 @@ class TestNativeLinuxRootResolution:
         for where, impl in _impls().items():
             assert self._run(impl, bundle_dir, present) == ["/opt/rocm/lib64"], where
 
+    def test_nested_llvm_runtime_follows_system_rocm_lib(self, bundle_dir):
+        """#7446: libamd_comgr depends on ROCm's versioned LLVM runtime, which is
+        installed below lib/llvm/lib rather than directly in lib."""
+        present = {
+            "/dev/kfd",
+            "/opt/rocm/lib/libhsa-runtime64.so",
+            "/opt/rocm/lib/llvm/lib",
+        }
+        for where, impl in _impls().items():
+            assert self._run(impl, bundle_dir, present) == [
+                "/opt/rocm/lib",
+                "/opt/rocm/lib/llvm/lib",
+            ], where
+
+    def test_lib64_host_still_finds_llvm_under_lib(self, bundle_dir):
+        """ROCm puts LLVM under <root>/lib/llvm even where HSA lives in lib64, so
+        deriving the llvm dir from the HSA dir alone would miss it and leave
+        libamd_comgr binding to the bundle's libLLVM."""
+        present = {
+            "/dev/kfd",
+            "/opt/rocm/lib64/libhsa-runtime64.so",
+            "/opt/rocm/lib/llvm/lib",
+        }
+        for where, impl in _impls().items():
+            assert self._run(impl, bundle_dir, present) == [
+                "/opt/rocm/lib64",
+                "/opt/rocm/lib/llvm/lib",
+            ], where
+
+    def test_lib64_host_prefers_its_own_llvm_dir_when_both_exist(self, bundle_dir):
+        present = {
+            "/dev/kfd",
+            "/opt/rocm/lib64/libhsa-runtime64.so",
+            "/opt/rocm/lib64/llvm/lib",
+            "/opt/rocm/lib/llvm/lib",
+        }
+        for where, impl in _impls().items():
+            assert self._run(impl, bundle_dir, present) == [
+                "/opt/rocm/lib64",
+                "/opt/rocm/lib64/llvm/lib",
+                "/opt/rocm/lib/llvm/lib",
+            ], where
+
+    def test_llvm_path_that_is_a_file_is_not_prepended(self, tmp_path, bundle_dir):
+        """Real filesystem: the serve-time caller joins these straight into
+        LD_LIBRARY_PATH without an is-dir filter, so a non-directory must not
+        reach it."""
+        root = tmp_path / "rocm"
+        (root / "lib").mkdir(parents = True)
+        (root / "lib" / "libhsa-runtime64.so").write_text("")
+        (root / "lib" / "llvm").mkdir()
+        (root / "lib" / "llvm" / "lib").write_text("not a directory")
+        real_exists = os.path.exists
+        # Pin both device nodes: a WSL test host really has /dev/dxg, which would
+        # take the WSL early-return and make this pass for the wrong reason.
+        pinned = {"/dev/kfd": True, "/dev/dxg": False}
+
+        def _exists(p):
+            return pinned.get(str(p), None) if str(p) in pinned else real_exists(p)
+
+        # A test host may itself have a real /opt/rocm (the default candidate), so
+        # assert on the bogus entry rather than on the whole list.
+        for where, impl in _impls().items():
+            with (
+                patch.object(sys, "platform", "linux"),
+                patch.dict(os.environ, {"ROCM_PATH": str(root)}, clear = True),
+                patch("os.path.exists", _exists),
+            ):
+                out = impl(str(bundle_dir))
+            assert str(root / "lib") in out, where
+            assert str(root / "lib" / "llvm" / "lib") not in out, where
+
     def test_lib_precedes_lib64_when_both_exist(self, bundle_dir):
         present = {
             "/dev/kfd",