Fixed a build target problem (#971)

Author: Amaras

sconscripts/coconut_SConscript

@@ -1,6 +1,6 @@
 Import('files_to_compile env')
 
 for file_info in files_to_compile:
-    build_target = f'#/build/{file_info.language}/{file_info.chapter}/{file_info.path.stem}'
+    build_target = f'#/build/{file_info.language}/{file_info.chapter}/{file_info.path.stem}.py'
     build_result = env.Coconut(build_target, str(file_info.path))
     env.Alias(str(file_info.chapter), build_result)