replace Julia's gcc dlls with WinRPM versions during deps/build.jl

[tkelman]

handle failure somewhat gracefully, provide informative messages

@vtjnash @ihnorton if no objections I'll want to merge and tag this pretty soon, works on my machine for both 32 and 64 bit, and I think I've handled failure cases here

[ihnorton]

yipes. well i guess this is the least bad option, thanks. i'm a little bit surprised that this works for the gcc libs, which presumably are open when julia is running.

[vtjnash]

would be helpful to still include the error message here

[tkelman]

would that just be catch err, and add a line "Error was: $err\n" * in the warning?

[vtjnash]

Or Base.show_error()

[tkelman]

@ihnorton I'm a little surprised too, I was thinking we'd have to do something trickier. The old dll's are still loaded in memory by Julia, so you do need to restart Julia to actually fix the issue.

I'm going to try to write a build-time mini-WinRPM to get these dll's from opensuse in the first place for the binaries.

@vtjnash I'll commit the following if it LGTY

        catch err
            buf = PipeBuffer()
            showerror(buf, err)
            warn("Could not update Julia's gcc dlls, some WinRPM packages may not work.\n" *
                "Error was: $(readall(buf))\n" *
                "Try running Julia as administrator and calling `Pkg.build(\"WinRPM\")`.")
        end

[vtjnash]

lgtm