(os/execute args &opts flags env)
Execute a program on the system and pass it string arguments. Flags is
a keyword that modifies how the program will execute.
:e - enables passing an environment to the program. Without :e, the
current environment is inherited.
:p - allows searching the current PATH for the binary to execute.
Without this flag, binaries must use absolute paths.
env is a table or struct mapping environment variables to values.
Returns the exit status of the program.