Extra compilers and the command set to "\n" would result in malformed
<Message> tags in vcxproj files. Those tags are used to display the
name of the extra compiler when building. Setting the extra compiler's
command to "\n" is a common trick to force the creation of the rule.
Make sure to trim the command name that is created from the extra
compiler's command to avoid such new-line-only bogus message tags.
Pick-to: 6.2 5.15
Change-Id: I1bae28ed14c438d777f96280c6b2cf5ca315b51c
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>