QtcProcess: Make exitMessage() a const method

Change-Id: Ibb0aaf0bf3bf216673646ea7b869fd7e55e6b81c
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/libs/utils/qtcprocess.cpp

@@ -1315,7 +1315,7 @@ QString QtcProcess::locateBinary(const QString &binary)
     as this will cause event loop problems.
 */
 
-QString QtcProcess::exitMessage()
+QString QtcProcess::exitMessage() const
 {
     const QString fullCmd = commandLine().toUserOutput();
     switch (result()) {

src/libs/utils/qtcprocess.h

@@ -182,7 +182,7 @@ public:
 
     QByteArray rawStdOut() const;
 
-    QString exitMessage();
+    QString exitMessage() const;
 
     QString toStandaloneCommandLine() const;