[ SOLVED ] Linux Mint 19.3 unable to compile latest Dev release

[nbohr1more]

Dev is failing to compile again:

make[1]: Entering directory '/home/user/dolphin-emu/Build/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_52c34.dir/src.cxx.o
/usr/bin/g++-9 -DFLAG_CXX_MISSING_VARIABLE_DECLARATIONS -Werror -Wmissing-variable-declarations -std=c++2a -o CMakeFiles/cmTC_52c34.dir/src.cxx.o -c /home/user/dolphin-emu/Build/CMakeFiles/CMakeTmp/src.cxx
g++-9: error: unrecognized command line option '-Wmissing-variable-declarations'; did you mean '-Wmissing-declarations'?
CMakeFiles/cmTC_52c34.dir/build.make:84: recipe for target 'CMakeFiles/cmTC_52c34.dir/src.cxx.o' failed
make[1]: *** [CMakeFiles/cmTC_52c34.dir/src.cxx.o] Error 1
make[1]: Leaving directory '/home/user/dolphin-emu/Build/CMakeFiles/CMakeTmp'
Makefile:140: recipe for target 'cmTC_52c34/fast' failed
make: *** [cmTC_52c34/fast] Error 2