Error compiling for gem5

Hello, When manually building from scratch, the compilation fails with the following config flags: BUILD_GEM5 BUILD_ARM with the "rampage" experiment.

rui@rui-laptop:~/repos/gitlab/fail/build$ make
Scanning dependencies of target fail-fsp
[  1%] Building CXX object src/core/sal/faultspace/CMakeFiles/fail-fsp.dir/BaseFaultSpace.cc.o
/usr/include/x86_64-linux-gnu/c++/9/bits/c++config.h:258: error: invalid declaration near token nullptr
/usr/include/x86_64-linux-gnu/c++/9/bits/c++config.h:276: error: invalid declaration near token namespace
/usr/include/x86_64-linux-gnu/c++/9/bits/c++config.h:280: error: invalid declaration near token namespace
/usr/include/c++/9/bits/cpp_type_traits.h:185: error: char16_t undeclared here
/usr/include/c++/9/bits/cpp_type_traits.h:192: error: char32_t undeclared here
/usr/include/c++/9/ext/type_traits.h:162: error: __is_null_pointer already defined....

Attached, there is the CMakeCache file.CMakeCache.txt