build: set STATIC_ANALYSIS when running via clang or coverity
build: set STATIC_ANALYSIS when running via clang or coverity

* configure.ac (STATIC_ANALYSIS): Define when run via clang's
scan-build or coverity-prevent's cov-build.
Use the CLANG_CC and COVERITY_BUILD_COMMAND envvars as witnesses.

siboulet/libvirt-openvz,danwent/libvirt-ovs,taget/libvirt,jfehlig/libvirt,siboulet/libvirt-openvz,sshah-solarflare/Libvirt-PCI-passthrough-,agx/libvirt,andreabolognani/libvirt,amery/libvirt-vserver,wiedi/libvirt,elmarco/libvirt,elmarco/libvirt,wiedi/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,leilihh/libvirt,novel/fbsd-libvirt,rlaager/libvirt,agx/libvirt,emaste/libvirt,novel/fbsd-libvirt,zippy2/libvirt,eskultety/libvirt,rlaager/libvirt,siboulet/libvirt-openvz,nertpinx/libvirt,cbosdo/libvirt,zhlcindy/libvirt-1.1.4-maintain,nertpinx/libvirt,amery/libvirt-vserver,soulxu/libvirt-xuhj,agx/libvirt,zhlcindy/libvirt-1.1.4-maintain,rmarwaha/libvirt,wiedi/libvirt,crobinso/libvirt,andreabolognani/libvirt,iam-TJ/libvirt,nertpinx/libvirt,rmarwaha/libvirt1,kantai/libvirt-vfork,jeckersb/libvirt,datto/libvirt,amery/libvirt-vserver,leilihh/libvirt,cbosdo/libvirt,libvirt/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,crobinso/libvirt,rmarwaha/libvirt,novel/fbsd-libvirt,taget/libvirt,jardasgit/libvirt,cbosdo/libvirt,bjzhang/libvirt,bjzhang/libvirt,VenkatDatta/libvirt,kantai/libvirt-vfork,foomango/libvirt,andreabolognani/libvirt,emaste/libvirt,wiedi/libvirt,jeckersb/libvirt,datto/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,olafhering/libvirt,trainstack/libvirt,trainstack/libvirt,dumbbell/libvirt,zippy2/libvirt,dumbbell/libvirt,rmarwaha/libvirt1,soulxu/libvirt-xuhj,amery/libvirt-vserver,foomango/libvirt,cbosdo/libvirt,VenkatDatta/libvirt,foomango/libvirt,datto/libvirt,jfehlig/libvirt,olafhering/libvirt,jeckersb/libvirt,iam-TJ/libvirt,zippy2/libvirt,wiedi/libvirt,kantai/libvirt-vfork,libvirt/libvirt,zhlcindy/libvirt-1.1.4-maintain,zippy2/libvirt,cbosdo/libvirt,kantai/libvirt-vfork,trainstack/libvirt,danwent/libvirt-ovs,elmarco/libvirt,warewolf/libvirt,shugaoye/libvirt,jardasgit/libvirt,amery/libvirt-vserver,shugaoye/libvirt,rmarwaha/libvirt1,usc-isi/libvirt,rlaager/libvirt,rmarwaha/libvirt1,fabianfreyer/libvirt,jeckersb/libvirt,taget/libvirt,rbu/libvirt,eskultety/libvirt,jfehlig/libvirt,trainstack/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,wiedi/libvirt,siboulet/libvirt-openvz,eskultety/libvirt,nertpinx/libvirt,emaste/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,agx/libvirt,usc-isi/libvirt,bjzhang/libvirt,dumbbell/libvirt,rbu/libvirt,trainstack/libvirt,jeckersb/libvirt,warewolf/libvirt,olafhering/libvirt,jardasgit/libvirt,novel/fbsd-libvirt,agx/libvirt,nertpinx/libvirt,foomango/libvirt,usc-isi/libvirt,jardasgit/libvirt,dumbbell/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,iam-TJ/libvirt,trainstack/libvirt,jeckersb/libvirt,datto/libvirt,jeckersb/libvirt,iam-TJ/libvirt,wiedi/libvirt,usc-isi/libvirt,warewolf/libvirt,fabianfreyer/libvirt,crobinso/libvirt,rmarwaha/libvirt1,emaste/libvirt,iam-TJ/libvirt,novel/fbsd-libvirt,foomango/libvirt,warewolf/libvirt,soulxu/libvirt-xuhj,datto/libvirt,eskultety/libvirt,fabianfreyer/libvirt,bjzhang/libvirt,zhlcindy/libvirt-1.1.4-maintain,sshah-solarflare/Libvirt-PCI-passthrough-,andreabolognani/libvirt,leilihh/libvirt,elmarco/libvirt,crobinso/libvirt,shugaoye/libvirt,leilihh/libvirt,danwent/libvirt-ovs,siboulet/libvirt-openvz,soulxu/libvirt-xuhj,soulxu/libvirt-xuhj,elmarco/libvirt,danwent/libvirt-ovs,rbu/libvirt,leilihh/libvirt,dumbbell/libvirt,trainstack/libvirt,eskultety/libvirt,emaste/libvirt,emaste/libvirt,emaste/libvirt,warewolf/libvirt,usc-isi/libvirt,novel/fbsd-libvirt,VenkatDatta/libvirt,olafhering/libvirt,rmarwaha/libvirt,novel/fbsd-libvirt,rbu/libvirt,leilihh/libvirt,libvirt/libvirt,rlaager/libvirt,fabianfreyer/libvirt,dumbbell/libvirt,novel/fbsd-libvirt,warewolf/libvirt,rmarwaha/libvirt1,kantai/libvirt-vfork,warewolf/libvirt,rmarwaha/libvirt,danwent/libvirt-ovs,rmarwaha/libvirt,bjzhang/libvirt,rbu/libvirt,novel/fbsd-libvirt,iam-TJ/libvirt,iam-TJ/libvirt,shugaoye/libvirt,sshah-solarflare/Libvirt-PCI-passthrough-,rmarwaha/libvirt,taget/libvirt,taget/libvirt,libvirt/libvirt