Fix Makefile configuration by env var support

example/Makefile

@@ -2,12 +2,12 @@
 # iniparser tests Makefile
 #
 
-CC      = gcc
-CFLAGS  = -g -I../src
-LFLAGS  = -L.. -liniparser
-AR	    = ar
-ARFLAGS = rcv
-RM      = rm -f
+CC      ?= gcc
+CFLAGS  += -g -I../src
+LFLAGS  += -L.. -liniparser
+AR	    ?= ar
+ARFLAGS += rcv
+RM      ?= rm -f
 
 
 default: all

test/Makefile

@@ -11,8 +11,9 @@ SRC = $(shell ls *.c | sed 's/AllTests.c//')
 OBJ = $(SRC:.c=.o)
 
 INCLUDE = -I../src
-CFLAGS  = -pipe -ansi -pedantic -Wall -Wextra -g
-LDFLAGS =
+CFLAGS  += -pipe -ansi -pedantic -Wall -Wextra -g
+LDFLAGS +=
+
 all: check
 
 check: testrun