simplify run_interactive, pipeline can now accept an IOBuffer

[KristofferC]

julia> io = IOBuffer();

julia> run(pipeline(`echo hello`; stdout=io))
Process(`echo hello`, ProcessExited(0))

julia> String(take!(io))
"hello\n"

[giordano]

pipeline can now accept an IOBuffer

"now" being "since Julia 1.1" apparently 😄

[giordano]

With this PR:

julia> io = IOBuffer(); run_interactive(preferred_runner()(mktempdir(); platform=Platform("x86_64", "linux"; libc="musl")), `/bin/bash -c "echo \$PATH"`, stdout=io); String(take!(io))
/opt/bin/x86_64-linux-musl-libgfortran3-cxx03:/opt/x86_64-linux-musl/bin:/opt/bin/x86_64-linux-musl-cxx11:/opt/x86_64-linux-musl/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/workspace/x86_64-linux-musl-cxx11/destdir/bin:/workspace/destdir/bin
""

If I revert it:

julia> io = IOBuffer(); run_interactive(preferred_runner()(mktempdir(); platform=Platform("x86_64", "linux"; libc="musl")), `/bin/bash -c "echo \$PATH"`, stdout=io); String(take!(io))
"/opt/bin/x86_64-linux-musl-libgfortran3-cxx03:/opt/x86_64-linux-musl/bin:/opt/bin/x86_64-linux-musl-cxx11:/opt/x86_64-linux-musl/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/workspace/x86_64-linux-musl-cxx11/destdir/bin:/workspace/destdir/bin\n"

I guess this wasn't covered by tests

[KristofferC]

Yeah... I was sure I tested it locally but I must have messed something up... I'm looking at it now. Feel free to revert in the meantime if it is causing trouble (it probably will...).