Shift it to the phase that requires it; SANDBOX_DISABLE in the global scope turns off the sandbox during depends phase which is extremely evil.
There must be more to the story. I moved SANDBOX_DISABLED to the src_compile and also src_install sections of the ebuild (eg. src_compile() { export SANDBOX_DISABLED=1 ...}) and the build fails as if the sandbox is active. So please advise further.
export SANDBOX_ON=0 SANDBOX_DISABLE is a worthless var that just toggles that :)
Thanks. Fixed in portage for dev-lisp/gcl.