Python extension module finally works on Windows.

test cases/python3/2 extmodule/ext/meson.build

@@ -1,6 +1,9 @@
 if host_machine.system() == 'darwin'
   # Default suffix is 'dylib' but Python does not use for extensions.
   suffix = 'so'
+elif host_machine.system() == 'windows'
+  # On Windows the extension is pyd for some unexplainable reason.
+  suffix = 'pyd'
 else
   suffix = []
 endif

test cases/python3/2 extmodule/meson.build

@@ -1,4 +1,7 @@
-project('Python extension module', 'c')
+project('Python extension module', 'c',
+  default_options : ['buildtype=release'])
+# Because Windows Python ships only with optimized libs,
+# we must build this project the same way.
 
 py3_dep = dependency('python3')
 

test cases/python3/3 cython/libdir/meson.build

@@ -1,3 +1,13 @@
+if host_machine.system() == 'darwin'
+  # Default suffix is 'dylib' but Python does not use for extensions.
+  suffix = 'so'
+elif host_machine.system() == 'windows'
+  # On Windows the extension is pyd for some unexplainable reason.
+  suffix = 'pyd'
+else
+  suffix = []
+endif
+
 pyx_c = custom_target('storer_pyx',
   output : 'storer_pyx.c',
   input : 'storer.pyx',
@@ -7,6 +17,7 @@ pyx_c = custom_target('storer_pyx',
 slib = shared_library('storer',
   'storer.c', pyx_c,
   name_prefix : '',
+  name_suffix : suffix,
   dependencies : py3_dep)
 
 pydir = meson.current_build_dir()