Fix cli caching spec to not fail when PWD contains hyphen
Fix cli caching spec to not fail when PWD contains hyphen

When the current working directory (returned by `fs.get_current_dir()`)
contains a hyphen (e.g. /home/flynn/luacheck-0.22.0), the spec
"cli caching caches results" fails, because "-" is interpreted as
pattern item.

This commit fixes this problem by escaping "-" together with "[" and
"]" inside the template after abspath{...} is substituted.

xpol/luacheck,mpeterv/luacheck,mpeterv/luacheck,xpol/luacheck,mpeterv/luacheck,xpol/luacheck