fastgltf fails to build on 10.15: error: 'To' does not refer to a value

[barracuda156]

In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/src/base64.cpp:37:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/base64.hpp:34:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/types.hpp:41:
/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/util.hpp:369:35: error: 'To' does not refer to a value
        return __builtin_bit_cast(To, from);
                                  ^
/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/util.hpp:366:23: note: declared here
    template<typename To, typename From>
                      ^
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/src/fastgltf.cpp:55:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/core.hpp:32:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/types.hpp:41:
/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/util.hpp:369:35: error: 'To' does not refer to a value
        return __builtin_bit_cast(To, from);
                                  ^
/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_graphics_fastgltf/fastgltf/work/fastgltf-0.7.0/include/fastgltf/util.hpp:366:23: note: declared here
    template<typename To, typename From>
                      ^
1 error generated.

See: ​https://build.macports.org/builders/ports-10.15_x86_64-builder/builds/174202/steps/install-port/logs/stdio

It also seems to need filesystem on < 10.14: ​https://build.macports.org/builders/ports-10.14_x86_64-builder/builds/198167/steps/install-port/logs/stdio