Switch the default for building GlobalISel.

Now, GlobalISel will be built by default. To turn that off, one has to
use -DLLVM_BUILD_GLOBAL_ISEL=OFF on the cmake command line.

<rdar://problem/30004433>

llvm-svn: 293232
GitOrigin-RevId: 00dd7172b5990bd8fcce97259a192200435a7612
1 file changed