When using -DLLVM_ENABLED_RUNTIMES instead of -DLLVM_ENABLED_PROJECTS
the llvm-omp-device-info tool is not compiled or installed.
In general, no llvm tool would be build on runtimes, because the
-DLLVM_BUILD_TOOLS flag is removed by the way runtimes compilation calls
This patch is simple. Just forward the value of this flag to the
runtime cmake command.
I'm also removing an unnecessary comment in the compilation of the tool