Need better error message for missing `--` after `-l` or `--timeline`

[jkwack]

When I missed -- after -l or--timeline, I got the following error message:

/opt/aurora/26.26.0/spack/unified/1.1.1/install/linux-x86_64/thapi-git.426c8097e536fe40a8148bb83787ea695c91c57a_0.0.12-git.113-vzj7hwg/bin/iprof:101:in `popen': wrong number of arguments (given 0, expected 1+) (ArgumentError)

  IO.popen(env, cmd) do |io|
           ^^^^^^^^
	from /opt/aurora/26.26.0/spack/unified/1.1.1/install/linux-x86_64/thapi-git.426c8097e536fe40a8148bb83787ea695c91c57a_0.0.12-git.113-vzj7hwg/bin/iprof:101:in `launch_usr_bin'
	from /opt/aurora/26.26.0/spack/unified/1.1.1/install/linux-x86_64/thapi-git.426c8097e536fe40a8148bb83787ea695c91c57a_0.0.12-git.113-vzj7hwg/bin/iprof:974:in `block in all_trace_and_processing'
	from /opt/aurora/26.26.0/spack/unified/1.1.1/install/linux-x86_64/thapi-git.426c8097e536fe40a8148bb83787ea695c91c57a_0.0.12-git.113-vzj7hwg/bin/iprof:469:in `open'
	from /opt/aurora/26.26.0/spack/unified/1.1.1/install/linux-x86_64/thapi-git.426c8097e536fe40a8148bb83787ea695c91c57a_0.0.12-git.113-vzj7hwg/bin/iprof:966:in `all_trace_and_processing'
	from /opt/aurora/26.26.0/spack/unified/1.1.1/install/linux-x86_64/thapi-git.426c8097e536fe40a8148bb83787ea695c91c57a_0.0.12-git.113-vzj7hwg/bin/iprof:1121:in `<main>'
x1921c0s1b0n0-hsn0.hsn.cm.sunspot.alcf.anl.gov: rank 0 exited with code 1
x1921c0s1b0n0-hsn0.hsn.cm.sunspot.alcf.anl.gov: rank 2 died from signal 15

If the error message suggests to add -- after -l or --timeline, users will be able to fix the issue easily.