build: disable dtrace on non-Linux builds
build: disable dtrace on non-Linux builds

Using dtrace (and systemtap in general) is Linux-specific.
Running ./autobuild.sh shows that attempting a cross-build to
target mingw was mistakenly trying to build dtrace code, merely
because it was present on the compilation host.

* configure.ac (with_dtrace): Don't attempt to use dtrace when
doing a cross-build hosted on Linux but targetting elsewhere.
Reported by Daniel P. Berrange.

fabianfreyer/libvirt,rmarwaha/libvirt1,fabianfreyer/libvirt,emaste/libvirt,jardasgit/libvirt,trainstack/libvirt,elmarco/libvirt,eskultety/libvirt,VenkatDatta/libvirt,libvirt/libvirt,iam-TJ/libvirt,shugaoye/libvirt,libvirt/libvirt,bjzhang/libvirt,shugaoye/libvirt,zhlcindy/libvirt-1.1.4-maintain,iam-TJ/libvirt,agx/libvirt,zippy2/libvirt,jeckersb/libvirt,crobinso/libvirt,taget/libvirt,iam-TJ/libvirt,rmarwaha/libvirt,olafhering/libvirt,zhlcindy/libvirt-1.1.4-maintain,iam-TJ/libvirt,olafhering/libvirt,datto/libvirt,foomango/libvirt,jeckersb/libvirt,jfehlig/libvirt,siboulet/libvirt-openvz,zippy2/libvirt,nertpinx/libvirt,crobinso/libvirt,nertpinx/libvirt,rlaager/libvirt,rmarwaha/libvirt1,dumbbell/libvirt,zippy2/libvirt,novel/fbsd-libvirt,nertpinx/libvirt,jeckersb/libvirt,novel/fbsd-libvirt,wiedi/libvirt,warewolf/libvirt,cbosdo/libvirt,warewolf/libvirt,agx/libvirt,siboulet/libvirt-openvz,zhlcindy/libvirt-1.1.4-maintain,cbosdo/libvirt,novel/fbsd-libvirt,wiedi/libvirt,elmarco/libvirt,cbosdo/libvirt,siboulet/libvirt-openvz,zippy2/libvirt,emaste/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,novel/fbsd-libvirt,jeckersb/libvirt,foomango/libvirt,jeckersb/libvirt,trainstack/libvirt,rmarwaha/libvirt1,jeckersb/libvirt,jfehlig/libvirt,danwent/libvirt-ovs,andreabolognani/libvirt,iam-TJ/libvirt,fabianfreyer/libvirt,foomango/libvirt,nertpinx/libvirt,wiedi/libvirt,andreabolognani/libvirt,emaste/libvirt,trainstack/libvirt,olafhering/libvirt,jardasgit/libvirt,emaste/libvirt,rmarwaha/libvirt,taget/libvirt,andreabolognani/libvirt,jardasgit/libvirt,danwent/libvirt-ovs,olafhering/libvirt,datto/libvirt,shugaoye/libvirt,datto/libvirt,iam-TJ/libvirt,VenkatDatta/libvirt,libvirt/libvirt,andreabolognani/libvirt,jfehlig/libvirt,crobinso/libvirt,warewolf/libvirt,trainstack/libvirt,wiedi/libvirt,datto/libvirt,eskultety/libvirt,datto/libvirt,emaste/libvirt,bjzhang/libvirt,taget/libvirt,shugaoye/libvirt,jeckersb/libvirt,dumbbell/libvirt,danwent/libvirt-ovs,dumbbell/libvirt,agx/libvirt,eskultety/libvirt,novel/fbsd-libvirt,warewolf/libvirt,warewolf/libvirt,elmarco/libvirt,agx/libvirt,iam-TJ/libvirt,cbosdo/libvirt,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,novel/fbsd-libvirt,rlaager/libvirt,danwent/libvirt-ovs,rmarwaha/libvirt1,emaste/libvirt,emaste/libvirt,VenkatDatta/libvirt,wiedi/libvirt,rmarwaha/libvirt,zhlcindy/libvirt-1.1.4-maintain,rmarwaha/libvirt1,cbosdo/libvirt,foomango/libvirt,trainstack/libvirt,novel/fbsd-libvirt,wiedi/libvirt,VenkatDatta/libvirt,dumbbell/libvirt,novel/fbsd-libvirt,rlaager/libvirt,bjzhang/libvirt,nertpinx/libvirt,eskultety/libvirt,siboulet/libvirt-openvz,foomango/libvirt,taget/libvirt,bjzhang/libvirt,novel/fbsd-libvirt,rmarwaha/libvirt1,trainstack/libvirt,taget/libvirt,rlaager/libvirt,bjzhang/libvirt,jardasgit/libvirt,warewolf/libvirt,warewolf/libvirt,wiedi/libvirt,libvirt/libvirt,danwent/libvirt-ovs,crobinso/libvirt,rmarwaha/libvirt,elmarco/libvirt,jfehlig/libvirt,eskultety/libvirt,shugaoye/libvirt,rmarwaha/libvirt,elmarco/libvirt,rmarwaha/libvirt,dumbbell/libvirt,dumbbell/libvirt,fabianfreyer/libvirt,agx/libvirt,andreabolognani/libvirt,siboulet/libvirt-openvz,trainstack/libvirt