In this instruction :"In order to start the build process, use "cd nss" and execute "make nss_build_all". By default this will produce a build in debug mode and for a 32-bit architecture. You may set the environment variable BUILD_OPT=1 to get an optimized build, and/or variable USE_64=1 to get a 64-bit build."
which command i use to set the environment variable BUILD_OPT=1 and USE_64=1 ???