HTR link failure on lassen

[seemamirch]

output from CI runs

test (metricTest.test.unitTest) ... /usr/workspace/stanf_ci/psaap-ci/artifacts/2449034/legion/bindings/regent/libregent.so: undefined reference to std::filesystem::directory_iterator::operator++()' /usr/workspace/stanf_ci/psaap-ci/artifacts/2449034/legion/bindings/regent/libregent.so: undefined reference to std::filesystem::directory_iterator::operator*() const'
/usr/workspace/stanf_ci/psaap-ci/artifacts/2449034/legion/bindings/regent/libregent.so: undefined reference to std::filesystem::path::has_root_directory() const' /usr/workspace/stanf_ci/psaap-ci/artifacts/2449034/legion/bindings/regent/libregent.so: undefined reference to std::filesystem::path::_M_split_cmpts()'
/usr/workspace/stanf_ci/psaap-ci/artifacts/2449034/legion/bindings/regent/libregent.so: undefined reference to std::filesystem::status(std::filesystem::path const&)' /usr/workspace/stanf_ci/psaap-ci/artifacts/2449034/legion/bindings/regent/libregent.so: undefined reference to std::filesystem::directory_iterator::directory_iterator(std::filesystem::path const&, std::filesystem::directory_options, std::error_code*)'
/usr/workspace/stanf_ci/psaap-ci/artifacts/2449034/legion/bindings/regent/libregent.so: undefined reference to `std::filesystem::path::has_filename() const'
collect2: error: ld returned 1 exit status

1. -lstdc++fs is explicitly needed on lassen
2. Failed with multiple gcc compilers

[lightsighter]

Assigning @eddy16112 since it seems like Realm has added the dependence for std::filesystem in realm/hardware_topology.cc.