This is another step to prevent writing out sensitive information to disk.
Typically, when running an external command, Vim writes the command input (the
buffer in this case) to a file in a private temp directory. When
'noshelltemp' is set and the system supports it, Vim uses pipes to the child
process to handle this instead.
Signed-off-by: James Vega <vega.james@gmail.com>