Fixed the issue that did not allow building TLM.
Build commands:
```bash
scons build/ARM/gem5.opt
scons setconfig build/ARM USE_SYSTEMC=n
scons --with-cxx-config --without-python --without-tcmalloc build/ARM/libgem5_opt.so
cd util/tlm
scons
```
Following this README, I tested it successfully with the simple examples:
https://gem5.googlesource.com/public/gem5/+/master/util/tlm/README
GitHub Issue: #591
Change-Id: If07fae2eb20ad62627e733573f61bc42d594f970
---------
Co-authored-by: Ivana Mitrovic <ivanamit91@gmail.com>