cmake: Install llvm-tblgen again

It was removed in r189130, but it turns out this makes life hard for
folks packaging LLVM and Clang and building the latter based on the
LLVM package.

Note that this only adds back the LLVM tblgen, and it's obviously
not included when LLVM_INSTALL_TOOLCHAIN_ONLY is set.

llvm-svn: 190419

cmake/modules/TableGen.cmake

@@ -136,4 +136,8 @@ macro(add_tablegen target project)
   if( LLVM_ENABLE_THREADS AND HAVE_LIBPTHREAD AND NOT BEOS )
     target_link_libraries(${target} pthread)
   endif()
+
+  if (${project} STREQUAL LLVM AND NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
+    install(TARGETS ${target} RUNTIME DESTINATION bin)
+  endif()
 endmacro()