Change the cp system command used for Windows

[daniel-thom]

In Julia 1.5.3 the invalid command was causing terminal display issues in Windows Cmd and PowerShell terminals.

Julia 1.5.3

julia> run(`cp`)
cp: missing file operand
Try 'cp --help' for more information.
[91m[1mERROR: [22m[39m[91mfailed process: Process(`[4mcp[24m`, ProcessExited(1)) [1][39m

Stacktrace:
[1] [1mpipeline_error[22m at [1m.\process.jl:525[22m [inlined]
[2] [1mrun[22m[1m([22m::Cmd; wait::Bool[1m)[22m at [1m.\process.jl:440[22m
[3] [1mrun[22m[1m([22m::Cmd[1m)[22m at [1m.\process.jl:438[22m
[4] top-level scope at [1mREPL[1]:1[22m

Julia 1.5.0

julia> run(`cp`)
cp: missing file operand
Try 'cp --help' for more information.
ERROR: failed process: Process(`cp`, ProcessExited(1)) [1]

Stacktrace:
[1] pipeline_error at .\process.jl:525 [inlined]
[2] run(::Cmd; wait::Bool) at .\process.jl:440
[3] run(::Cmd) at .\process.jl:438
[4] top-level scope at REPL[1]:1

[codecov[bot]]

Codecov Report

Merging #203 (5698695) into master (34940bd) will decrease coverage by 2.74%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #203      +/-   ##
==========================================
- Coverage   74.55%   71.81%   -2.75%     
==========================================
  Files          42       42              
  Lines        3018     2696     -322     
==========================================
- Hits         2250     1936     -314     
+ Misses        768      760       -8     

Flag	Coverage Δ
unittests	71.81% <100.00%> (-2.75%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/utils/utils.jl	56.42% <100.00%> (-3.17%)	:arrow_down:
src/utils/assert_op.jl	44.44% <0.00%> (-13.89%)	:arrow_down:
src/utils/test.jl	42.30% <0.00%> (-7.70%)	:arrow_down:
src/single_time_series.jl	59.74% <0.00%> (-7.29%)	:arrow_down:
src/time_series_container.jl	53.65% <0.00%> (-6.76%)	:arrow_down:
src/serialization.jl	44.44% <0.00%> (-6.06%)	:arrow_down:
src/internal.jl	70.73% <0.00%> (-5.87%)	:arrow_down:
src/deterministic_metadata.jl	5.00% <0.00%> (-4.53%)	:arrow_down:
src/forecasts.jl	84.37% <0.00%> (-4.00%)	:arrow_down:
src/time_series_parser.jl	64.78% <0.00%> (-3.97%)	:arrow_down:
... and 27 more