use -O1 optimization level for gcc 4.2
use -O1 optimization level for gcc 4.2

gcc (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu4) seems to miscopile isl with -O2

inducer/isl-mirror,UBERTC/isl,jleben/isl,tobig/isl,VanirLLVM/toolchain_isl,SaberMod/isl-current,pierrotdelalune/isl,SaberMod/isl-current,inducer/isl-mirror,tobig/isl,Meinersbur/isl,pierrotdelalune/isl,evaautomation/isl,crossbuild/isl,PollyLabs/isl,simbuerg/isl,cfx-next/toolchain_isl-upstream,inducer/isl-mirror,epowers/isl,tobig/isl,Distrotech/isl,crossbuild/isl,jleben/isl,UBERTC/isl,cfx-next/toolchain_isl-upstream,abduld/isl,cfx-next/toolchain_isl-upstream,crossbuild/isl,BenzoSM/isl,tobig/isl,nicolasvasilache/isl,jleben/isl,BobSaget-Mod/libisl,BobSaget-Mod/libisl,simbuerg/isl,serge-sans-paille/isl,serge-sans-paille/isl,Distrotech/isl,Distrotech/isl,pierrotdelalune/isl,serge-sans-paille/isl,KangDroidSMProject/ISL,KangDroidSMProject/ISL,BenzoSM/isl,nicolasvasilache/isl,simbuerg/isl,VanirLLVM/toolchain_isl,inducer/isl-mirror,UBERTC/isl,pierrotdelalune/isl,Meinersbur/isl,epowers/isl,BobSaget-Mod/libisl,nicolasvasilache/isl,VanirLLVM/toolchain_isl,abduld/isl,crossbuild/isl,BenzoSM/isl,KangDroidSMProject/ISL,cfx-next/toolchain_isl-upstream,simbuerg/isl,BenzoSM/isl,jleben/isl,PollyLabs/isl,evaautomation/isl,abduld/isl,nicolasvasilache/isl,simbuerg/isl,evaautomation/isl,KangDroidSMProject/ISL,inducer/isl-mirror,UBERTC/isl,VanirLLVM/toolchain_isl,epowers/isl,cfx-next/toolchain_isl-upstream,serge-sans-paille/isl,PollyLabs/isl,PollyLabs/isl,pierrotdelalune/isl,Meinersbur/isl,epowers/isl,evaautomation/isl,PollyLabs/isl,SaberMod/isl-current,jleben/isl,serge-sans-paille/isl,KangDroidSMProject/ISL,BobSaget-Mod/libisl,SaberMod/isl-current,BobSaget-Mod/libisl,BenzoSM/isl,Distrotech/isl,abduld/isl,Meinersbur/isl,epowers/isl,VanirLLVM/toolchain_isl,nicolasvasilache/isl,Distrotech/isl