Fix naming of ABI3 extension libraries on Windows

This commit fixes the naming conventions of ABI3 builds on Windows. It
also adopts a recent CMake/FindPython interface whenever available.

cmake/nanobind-config.cmake

@@ -4,20 +4,34 @@ if (NOT TARGET Python::Module)
   message(FATAL_ERROR "You must invoke 'find_package(Python COMPONENTS Interpreter Development REQUIRED)' prior to including nanobind.")
 endif()
 
-# Determine the Python extension suffix and stash in the CMake cache
-execute_process(
-  COMMAND "${Python_EXECUTABLE}" "-c"
-    "import sysconfig; print(sysconfig.get_config_var('EXT_SUFFIX'))"
-  RESULT_VARIABLE NB_SUFFIX_RET
-  OUTPUT_VARIABLE NB_SUFFIX
-  OUTPUT_STRIP_TRAILING_WHITESPACE)
-
-if (NB_SUFFIX_RET AND NOT NB_SUFFIX_RET EQUAL 0)
-  message(FATAL_ERROR "nanobind: Python sysconfig query to "
-    "find 'EXT_SUFFIX' property failed!")
+# Determine the the right suffix for ordinary and stable ABI extensions
+if (CMAKE_VERSION VERSION_GREATER_EQUAL 3.26)
+  set(NB_SUFFIX   ${Python_SOABI})
+  set(NB_SUFFIX_S ${Python_SOSABI})
+else()
+  # Determine the Python extension suffix and stash in the CMake cache
+  execute_process(
+    COMMAND "${Python_EXECUTABLE}" "-c"
+      "import sysconfig; print(sysconfig.get_config_var('EXT_SUFFIX'))"
+    RESULT_VARIABLE NB_SUFFIX_RET
+    OUTPUT_VARIABLE NB_SUFFIX
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+  if (NB_SUFFIX_RET AND NOT NB_SUFFIX_RET EQUAL 0)
+    message(FATAL_ERROR "nanobind: Python sysconfig query to "
+      "find 'EXT_SUFFIX' property failed!")
+  endif()
+
+  get_filename_component(NB_SUFFIX_EXT "${NB_SUFFIX}" LAST_EXT)
+  if (WIN32)
+    set(NB_SUFFIX_S ".${NB_SUFFIX_EXT}")
+  else()
+    set(NB_SUFFIX_S ".abi3${NB_SUFFIX_EXT}")
+  endif()
 endif()
 
-set(NB_SUFFIX ${NB_SUFFIX} CACHE INTERNAL "")
+set(NB_SUFFIX   ${NB_SUFFIX}   CACHE INTERNAL "")
+set(NB_SUFFIX_S ${NB_SUFFIX_S} CACHE INTERNAL "")
 
 get_filename_component(NB_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
 get_filename_component(NB_DIR "${NB_DIR}" PATH)
@@ -194,8 +208,7 @@ function(nanobind_extension name)
 endfunction()
 
 function(nanobind_extension_abi3 name)
-  get_filename_component(ext "${NB_SUFFIX}" LAST_EXT)
-  set_target_properties(${name} PROPERTIES PREFIX "" SUFFIX ".abi3${ext}")
+  set_target_properties(${name} PROPERTIES PREFIX "" SUFFIX "${NB_SUFFIX_S}")
 endfunction()
 
 function (nanobind_lto name)