Windows: Add PATH to .dll directories

Python 3.8+ on Windows: DLL search paths for dependent
shared libraries.

Refs.:
- python/cpython#80266
- https://docs.python.org/3.8/library/os.html#os.add_dll_directory

.github/workflows/windows.yml

@@ -58,4 +58,5 @@ jobs:
         if(!$?) { Exit $LASTEXITCODE }
     - name: Unit tests
       run: |
+        set PATH="C:/Program Files (x86)/pyAMReX/bin/;%PATH%"
         ctest --test-dir build -C Debug --output-on-failure

src/amrex/__init__.py

@@ -1,3 +1,21 @@
+import os
+
+# Python 3.8+ on Windows: DLL search paths for dependent
+# shared libraries
+# Refs.:
+# - https://github.com/python/cpython/issues/80266
+# - https://docs.python.org/3.8/library/os.html#os.add_dll_directory
+if os.name == "nt":
+    # add anything in the current directory
+    pwd = __file__.rsplit(os.sep, 1)[0] + os.sep
+    os.add_dll_directory(pwd)
+    # add anything in PATH
+    paths = os.environ.get("PATH", "")
+    for p in paths.split(";"):
+        if os.path.exists(p):
+            os.add_dll_directory(p)
+
+# import core bindings to C++
 from . import amrex_pybind
 from .amrex_pybind import *  # noqa