jsoncpp compilation error with gcc 7

[dunatotatos]

Hi,

When compiling strelka with gcc >= 7, I get the following error: /tmp/x_ahungler/spack-stage/spack-stage-strelka-2.8.2-czrel2avyz3nbiu2xs3tbesdjru5qnvn/spack-build-czrel2a/redist/jsoncpp-0.10.4/src/lib_json/json_reader.cpp:1087:5: error: this statement may fall through [-Werror=implicit-fallthrough=]

This issue has been closed on jsoncpp. Strelka may need to update the shipped in version of jsoncpp to include this fix.