In the code generated command-line, you’re missing a space before /build.
Change
pProcess.StartInfo.Arguments = "/@:Content/mgcb/" + pipeLineFile + "/build:E:/images/11098302195_9b9e9ac974_o.png";
to
pProcess.StartInfo.Arguments = "/@:Content/mgcb/" + pipeLineFile + " /build:E:/images/11098302195_9b9e9ac974_o.png";