Build: Fix missing CFLAGS (used for sqlite3 amalgamation only)

Makefile.conf

@@ -18,18 +18,23 @@ PREFIX?=$(HOME)
 # Constants
 CXXFLAGS+=-std=c++11 -fPIC -Wall -Wextra -pedantic
 CXXFLAGS+=-I$(PREFIX)/include
+CFLAGS+=-fPIC -pthread -DSQLITE_THREADSAFE=1
 LDFLAGS+=-L$(PREFIX)/lib
 
 ifneq (,$(findstring g++,$(CXX)))
     CXXFLAGS+=-fdiagnostics-color=always
+    CFLAGS+=-fdiagnostics-color=always
 else ifneq (,$(findstring clang,$(CXX)))
     CXXFLAGS+=-fcolor-diagnostics
+    CFLAGS+=-fcolor-diagnostics
 endif
 
 ifeq ($(DEBUG),1)
     CXXFLAGS+=-g -O0
+    CFLAGS+=-g -O0
 else
     CXXFLAGS+=-DNDEBUG=1 -O3
+    CFLAGS+=-DNDEBUG=1 -O3
 endif
 
 ifndef ENGINE_TEST