Use CFLAGS to build self-tests

test/Makefile

@@ -4,13 +4,13 @@ include ../Make.inc
 all: test-double test-float # test-double-system test-float-system
 
 test-double: test-double.c libm-test.c
-	$(CC) -g $@.c -D__BSD_VISIBLE -I ../include -I../src ../libopenlibm.a -o $@
+	$(CC) $(CFLAGS) -g $@.c -D__BSD_VISIBLE -I ../include -I../src ../libopenlibm.a -o $@
 
 test-float: test-float.c libm-test.c
-	$(CC) -g $@.c -D__BSD_VISIBLE -I ../include -I../src ../libopenlibm.a -o $@
+	$(CC) $(CFLAGS) -g $@.c -D__BSD_VISIBLE -I ../include -I../src ../libopenlibm.a -o $@
 
 test-double-system: test-double.c libm-test.c
-	$(CC) -g $< -DSYS_MATH_H -lm -o $@
+	$(CC) $(CFLAGS) -g $< -DSYS_MATH_H -lm -o $@
 
 test-float-system: test-float.c libm-test.c
-	$(CC) -g $< -DSYS_MATH_H -lm -o $@
+	$(CC) $(CFLAGS) -g $< -DSYS_MATH_H -lm -o $@