Get rid of QtcProcess::workingDirectory() overload

Adapt all callers' code so that it passes the FilePath
instead of QString. As a consequence introduce
TemporaryDirectory::masterDirectoryFilePath() and use
it where easily possible.

Change-Id: I14564949b3b916921e32a2957c84c03d1da43af2
Reviewed-by: hjk <hjk@qt.io>

src/plugins/projectexplorer/extracompiler.cpp

@@ -415,7 +415,7 @@ void ProcessExtraCompiler::runInThread(
 
     process.setEnvironment(env);
     if (!workDir.isEmpty())
-        process.setWorkingDirectory(workDir.toString());
+        process.setWorkingDirectory(workDir);
     process.setCommand({ cmd, args });
     process.setWriteData(sourceContents);
     process.start();