Create common.make with LOCAL_CFLAGS and friends

Create a common.make for definitions that are shared between tests/Makefile
and programs/Makefile, to facilitate maintenance. Start populating it with
CFLAGS/LDFLAGS variables. More to follow in subsequent commits.

Keep library/Makefile independent, at least for the time being.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

tests/Makefile

diff --git a/tests/Makefile b/tests/Makefile
index f242b51..3a6fd59 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -1,23 +1,12 @@
-
-# To compile on SunOS: add "-lsocket -lnsl" to LDFLAGS
-
-CFLAGS	?= -O2
-WARNING_CFLAGS ?= -Wall -Wextra -Wformat=2 -Wno-format-nonliteral
-LDFLAGS ?=
+include ../scripts/common.make
 
 # Set this to -v to see the details of failing test cases
 TEST_FLAGS ?= $(if $(filter-out 0 OFF Off off NO No no FALSE False false N n,$(CTEST_OUTPUT_ON_FAILURE)),-v,)
 
 default: all
 
-LOCAL_CFLAGS = $(WARNING_CFLAGS) -I$(MBEDTLS_TEST_PATH)/include -I../include -D_FILE_OFFSET_BITS=64
 # Also include library headers, for the sake of invasive tests.
 LOCAL_CFLAGS += -I../library
-LOCAL_LDFLAGS = ${MBEDTLS_TEST_OBJS} 		\
-		-L../library 			\
-		-lmbedtls$(SHARED_SUFFIX)	\
-		-lmbedx509$(SHARED_SUFFIX)	\
-		-lmbedcrypto$(SHARED_SUFFIX)
 
 include ../3rdparty/Makefile.inc
 LOCAL_CFLAGS+=$(THIRDPARTY_INCLUDES)