[CMake] Add llvm-tblgen to dependencies of check-llvm.

llvm-tblgen is not built when external LLVM_TABLEGEN is specified.
Even then, llvm-tblgen should be built for testing tblgen itself.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199558 91177308-0d34-0410-b5e6-96231b3b80d8

Author: chapuni

test/CMakeLists.txt

@@ -40,6 +40,7 @@ set(LLVM_TEST_DEPENDS
           llvm-readobj
           llvm-rtdyld
           llvm-symbolizer
+          llvm-tblgen
           macho-dump
           opt
           profile_rt-shared