Allow loading libhostfxr directly from the dotnet_root

This is a prerequisite to load self-contained components (which is still
not supported upstream, though).

Author: filmor

clr_loader/ffi/__init__.py

@@ -16,6 +16,7 @@
 
 def load_hostfxr(dotnet_root: Path):
     hostfxr_name = _get_dll_name("hostfxr")
+    dotnet_root = dotnet_root.absolute()
 
     # This will fail as soon as .NET hits version 10, but hopefully by then
     # we'll have a more robust way of finding the libhostfxr
@@ -28,6 +29,11 @@ def load_hostfxr(dotnet_root: Path):
         except Exception:
             pass
 
+    try:
+        return ffi.dlopen(str(dotnet_root / hostfxr_name))
+    except Exception:
+        pass
+
     raise RuntimeError(f"Could not find a suitable hostfxr library in {dotnet_root}")