Utils: Extract a CommandLine structure from a QtcProcess

We regularly pass around strings or filenames or pairs of strings
or filenames and stringlist etc the in the end will be used
as a kind of "command line", with quite a bit of ad-hoc user
code and QtcProcess::addArg etc to set them up and manipulate them.

Let's have a class for that concept.

Change-Id: I288ab939d853b32c717135a65242c584c2beab50
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/projectexplorer/runcontrol.cpp

@@ -1549,4 +1549,9 @@ void RunWorker::stop()
     reportStopped();
 }
 
+CommandLine Runnable::commandLine() const
+{
+    return CommandLine(FilePath::fromString(executable), commandLineArguments);
+}
+
 } // namespace ProjectExplorer