THRIFT-4496: python specific list of keywords for python generator (#1567)

Client: py
diff --git a/compiler/cpp/CMakeLists.txt b/compiler/cpp/CMakeLists.txt
index 5da28aa..e618877 100644
--- a/compiler/cpp/CMakeLists.txt
+++ b/compiler/cpp/CMakeLists.txt
@@ -62,6 +62,9 @@
     src/thrift/audit/t_audit.cpp
 )
 
+set(thrift_compiler_LANGS
+)
+
 # This macro adds an option THRIFT_COMPILER_${NAME}
 # that allows enabling or disabling certain languages
 macro(THRIFT_ADD_COMPILER name description initial)
@@ -70,6 +73,7 @@
     option(${enabler} ${description} ${initial})
     if(${enabler})
         list(APPEND thrift-compiler_SOURCES ${src})
+        list(APPEND thrift_compiler_LANGS ${name})
     endif()
 endmacro()