Could you please expose a way of setting environment variables for the toolchain, like we can for exec tasks? They use the same configuration for args, why not for environment variables? For instance we could do this:
cppCompiler.args "-fdiagnostics-color=always"
cppCompiler.args "-fmessage-length=80"
cppCompiler.args "-fno-diagnostics-show-option"
cppCompiler.environment("GCC_COLOR",
"error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01")