wrapper: use a private wine prefix

wrapper.py.in

@@ -121,6 +121,11 @@ if is_really_windows():
     depsdir.append("/usr/lib/gcc/x86_64-w64-mingw32/@CMAKE_CXX_COMPILER_VERSION@/")
     searchvar = 'WINEPATH'
     env['WINEDEBUG'] = '-all'
+
+    # Indicate that we want a local wine prefix in the build directory.
+    arch = env.get('WINEARCH', 'win64')
+    if not 'WINEPREFIX' in env:
+        env['WINEPREFIX'] = f"@CMAKE_CURRENT_BINARY_DIR@/{arch}"
 else:
     separator = ':'
     depsdir = ['lib', 'lib64']