Fix underquoted issues for run_command.sh (#613)

The --cfg argument can accept these format:
1) '--cfg=key="value"',
2) --cfg='key="value"'
3) --cfg=key=\"value\"

but --cfg=key="value" is invalid (no single quote, and also not escaping the double quote).

This CL fix this issue by put the entire --cfg=... string inside of a single quote.