test: pass process.env to child processes

For variables such as LD_LIBRARY_PATH and DYLD_LIBRARY_PATH that are
needed for dynamically linked binaries

PR-URL: https://github.com/nodejs/node/pull/16405


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>