Revert "Port to Qt 6's absence of QProcess::setupChildProcess"

This reverts commit 6a66ced594.

The patch that will introduce the alternative to setupChildProcess
(QProcess::setChildProcessModifier()) has not yet found its
way to qtbase and current Qt dev already identifies itself as
version 6.0.0, rendering the code here uncompilable.

Change-Id: I570b01598005070f0c17604226d245a3a381250e
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/ssh/sshprocess.cpp

@@ -47,12 +47,6 @@ SshProcess::SshProcess()
             env.set("DISPLAY", ":0");
     }
     setProcessEnvironment(env.toProcessEnvironment());
-
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0) && defined(Q_OS_UNIX)
-    setChildProcessModifier([]() {
-        setsid(); // Otherwise, ssh will ignore SSH_ASKPASS and read from /dev/tty directly.
-    });
-#endif
 }
 
 SshProcess::~SshProcess()
@@ -68,13 +62,11 @@ SshProcess::~SshProcess()
     waitForFinished(1000);
 }
 
-#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
 void SshProcess::setupChildProcess()
 {
 #ifdef Q_OS_UNIX
     setsid(); // Otherwise, ssh will ignore SSH_ASKPASS and read from /dev/tty directly.
 #endif
 }
-#endif
 
 } // namespace QSsh

src/libs/ssh/sshprocess.h

@@ -38,9 +38,7 @@ public:
     ~SshProcess() override;
 
 private:
-#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
     void setupChildProcess() override;
-#endif
 };
 
 } // namespace QSsh

src/libs/utils/qtcprocess.cpp

@@ -678,10 +678,6 @@ QtcProcess::QtcProcess(QObject *parent)
     static int qProcessProcessErrorMeta = qRegisterMetaType<QProcess::ProcessError>();
     Q_UNUSED(qProcessExitStatusMeta)
     Q_UNUSED(qProcessProcessErrorMeta)
-
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0) && defined(Q_OS_UNIX)
-    setChildProcessModifier([this]() { niceChildProcess(); });
-#endif
 }
 
 void QtcProcess::setUseCtrlCStub(bool enabled)
@@ -1224,25 +1220,18 @@ QString QtcProcess::expandMacros(const QString &str, AbstractMacroExpander *mx,
     return ret;
 }
 
-#if defined Q_OS_UNIX
-void QtcProcess::niceChildProcess()
+void QtcProcess::setupChildProcess()
 {
+#if defined Q_OS_UNIX
     // nice value range is -20 to +19 where -20 is highest, 0 default and +19 is lowest
     if (m_lowPriority) {
         errno = 0;
         if (::nice(5) == -1 && errno != 0)
             perror("Failed to set nice value");
     }
-}
-
-#  if QT_VERSION < QT_VERSION_CHECK(6,0,0)
-void QtcProcess::setupChildProcess()
-{
-    niceChildProcess();
+#endif
     QProcess::setupChildProcess();
 }
-#  endif
-#endif
 
 bool QtcProcess::ArgIterator::next()
 {

src/libs/utils/qtcprocess.h

@@ -142,12 +142,7 @@ public:
     };
 
 private:
-#ifdef Q_OS_UNIX
-#  if QT_VERSION < QT_VERSION_CHECK(6,0,0)
     void setupChildProcess() override;
-#  endif
-    void niceChildProcess();
-#endif
 
     CommandLine m_commandLine;
     Environment m_environment;

src/libs/utils/synchronousprocess.cpp

@@ -89,27 +89,19 @@ static Q_LOGGING_CATEGORY(processLog, "qtc.utils.synchronousprocess", QtWarningM
 // A special QProcess derivative allowing for terminal control.
 class TerminalControllingProcess : public QProcess {
 public:
-    TerminalControllingProcess()
-    {
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0) && defined(Q_OS_UNIX)
-        setChildProcessModifier([this]() { maybeSetsid(); });
-#endif
-    }
+    TerminalControllingProcess() = default;
 
     unsigned flags() const { return m_flags; }
     void setFlags(unsigned tc) { m_flags = tc; }
 
 protected:
-    inline void maybeSetsid();
-#if QT_VERSION < QT_VERSION_CHECK(6,0,0) && defined(Q_OS_UNIX)
-    void setupChildProcess() override { maybeSetsid(); }
-#endif
+    void setupChildProcess() override;
 
 private:
     unsigned m_flags = 0;
 };
 
-inline void TerminalControllingProcess::maybeSetsid()
+void TerminalControllingProcess::setupChildProcess()
 {
 #ifdef Q_OS_UNIX
     // Disable terminal by becoming a session leader.