build: factor the LolFx compilation rule into configure.ac.

neercs/Makefile.am

@@ -28,9 +28,5 @@ CLEANFILES = $(noinst_PROGRAMS:%$(EXEEXT)=%.self) \
 
 SUFFIXES = .lolfx
 .lolfx.o:
-	(echo "char const *"; \
+	$(LOLFX_BUILD)
-	 echo "lolfx_$(notdir $(basename $(filter %.lolfx, $^))) ="; \
-	 $(SED) 's/"/\\"/g' $(filter %.lolfx, $^) | \
-	 $(SED) 's/\([^\r]*\).*/"\1\\n"/'; \
-	 echo ";") | $(CXXCOMPILE) -xc++ -c - -o $@