tce-load -i compiletc meson 

wget https://github.com/open-source-parsers/jsoncpp/archive/refs/tags/1.9.5.tar.gz

cd jsoncpp-1.9.5

mkdir build
cd build

CC="gcc -flto -mtune=generic -Os -pipe" CXX="g++ -flto -mtune=generic -Os -pipe" meson --prefix=/usr/local --localstatedir=/var --buildtype=plain

[-fno-exceptions fails]

ninja [0m 11.93s]
sudo ninja install

jsoncpp 1.9.4 [?!]

  User defined options
    buildtype    : plain
    localstatedir: /var
    prefix       : /usr/local