JSON-124 make html_directory configurable via Makefile & macros, instead of echo

server/Makefile

@@ -102,9 +102,6 @@ $(TARGET_GTEST): unittest_json.o unittest_nfc.o unittest_decompose.o unittest_rp
 libjson-adapter.a: $(ALL_OBJECTS)
 	$(AR) rcs $@ $^
 
-prefix-config.cc:
-	echo '// This file is generated by make. Edit the Makefile, not this file!\n#include "prefix-config.hh" \nconst char* const html_directory = "html";\n' > $@
-
 gtest-all.o: $(GTEST_DIR)/src/gtest-all.cc
 	$(CXX) $(CPPFLAGS) -I$(GTEST_DIR) $(CXXFLAGS) -o $@ -c $<
 
@@ -145,7 +142,6 @@ clean:
 	rm -vf *.o json_spirit/*.o
 	rm -vf *.a json_spirit/*.a
 	rm -vf *.d json_spirit/*.d
-	rm -vf prefix-config.cc
 
 .PHONY: run
 run:

server/Makefile.conf

@@ -67,7 +67,9 @@ else ifeq ($(BUILD_FOR),Darwin)
     CXX=c++ -std=c++11 -fPIC
 endif
 
-CPPFLAGS=-isystem $(GTEST_DIR)/include
+HTML_DIR ?= "html"
+
+CPPFLAGS=-isystem $(GTEST_DIR)/include -DHTML_DIR=$(HTML_DIR)
 
 ifeq ($(BUILD_FOR),Linux)
     CXXFLAGS=-fstack-protector-all -fdiagnostics-color=always