[cmake] Drop clang-tools-extra from LLVM_ALL_PROJECTS
[cmake] Drop clang-tools-extra from LLVM_ALL_PROJECTS

We iterate over the list and only enable projects from that list that
are present in LLVM_ENABLE_PROJECTS and disable all other projects. Most
users will only specify clang in LLVM_ENABLE_PROJECTS and expect
clang-tools-extra to be implicitly enabled, so remove clang-tools-extra
from LLVM_ALL_PROJECTS so that it doesn't get disabled instead.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@353354 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm