Handle paths that start with 'C:/' #201

Job	Run time
leftovers	16s
coverage	36s
build	18s
compare (rails/rails, ubuntu)	24s
compare (rails/rails, windows)	2m 20s
rubocop	24s
spellr	18s
compare (rails/rails, macos)	52s
compare (ruby/ruby, ubuntu)	36s
rspec (2.7, ubuntu)	58s
compare (ruby/ruby, windows)	2m 59s
rspec (2.7, windows)	2m 12s
compare (ruby/ruby, macos)	1m 32s
rspec (2.7, macos)	1m 54s
compare (facebook/react, ubuntu)	22s
rspec (3.0, ubuntu)	27s
compare (facebook/react, windows)	3m 14s
rspec (3.0, windows)	1m 21s
compare (facebook/react, macos)	1m 6s
rspec (3.0, macos)	1m 22s
rspec (3.1, ubuntu)	31s
rspec (3.1, windows)	1m 46s
rspec (3.1, macos)	46s
rspec (3.2, ubuntu)	26s
rspec (3.2, windows)	2m 49s
rspec (3.2, macos)	46s
rspec (ruby-head, ubuntu)	28s
rspec (ruby-head, windows)	1m 42s
rspec (ruby-head, macos)	1m 28s
rspec (jruby-9.4, ubuntu)	1m 47s
rspec (jruby-9.4, windows)	4m 21s
rspec (jruby-9.4, macos)	6m 1s
rspec (jruby-head, ubuntu)	1m 48s
rspec (jruby-head, windows)	4m 24s
rspec (jruby-head, macos)	6m 14s
	58m 48s

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