In VARIABLES.CSV, RETAIN variable were only flagged as such for GLOBALS, now local POU variable shoud be as well.
include ../../common.mk
lib_LIBRARIES = libstage4_c.a
libstage4_c_a_SOURCES = generate_c.cc
libstage4_c_a_LIBADD = ../stage4.o
libstage4_c_a_CPPFLAGS = -I../../../absyntax