iperformance: replace = by := when it is constant shell call

git-svn-id: http://svn.eurecom.fr/openair4G/trunk@6200 818b1a75-f10b-46b9-bf7c-635c3b92a50f

common/utils/Makefile.inc

 export KERNEL_DIR=/lib/modules/$(shell uname -r)/
-CC=gcc
-CCC=gcc
-linux = $(shell if [ `uname` = "Linux" ] ; then echo "1" ; else echo "0" ; fi)
+CC=gcc-4.8
+CCC=gcc-4.8
+linux := $(shell if [ `uname` = "Linux" ] ; then echo "1" ; else echo "0" ; fi)
 
 #CFLAGS += -std=gnu99 
 CFLAGS += -Wall -g -ggdb -Wstrict-prototypes -fno-strict-aliasing