The global prefix is always one char. Don't use a string for it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195926 91177308-0d34-0410-b5e6-96231b3b80d8
[CMake] Let add_public_tablegen_target responsible to provide dependency to CommonTableGen.

add_public_tablegen_target adds *CommonTableGen to LLVM_COMMON_DEPENDS.
LLVM_COMMON_DEPENDS affects add_llvm_library (and other add_target stuff) within its scope.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195927 91177308-0d34-0410-b5e6-96231b3b80d8
[CMake] Also OptionTests can be free from add_dependencies() with add_public_tablegen_target().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195928 91177308-0d34-0410-b5e6-96231b3b80d8
[CMake] Let add_public_tablegen_target() provide intrinsics_gen, too.

I think, in principle, intrinsics_gen may be added explicitly.
That said, it can be added incidentally, since each target already has dependencies to llvm-tblgen.
Almost all source files depend on both CommonTaleGen and intrinsics_gen.

Explicit add_dependencies() have been pruned under lib/Target.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195929 91177308-0d34-0410-b5e6-96231b3b80d8