Makefile.am: only include piplib in distribution if it has been configured
Makefile.am: only include piplib in distribution if it has been configured

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