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
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bd5faac..5cb24ea 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -178,7 +178,7 @@
   endif()
 endif()
 
-option(LLVM_BUILD_GLOBAL_ISEL "Experimental: Build GlobalISel" OFF)
+option(LLVM_BUILD_GLOBAL_ISEL "Experimental: Build GlobalISel" ON)
 if(LLVM_BUILD_GLOBAL_ISEL)
   add_definitions(-DLLVM_BUILD_GLOBAL_ISEL)
 endif()