Fix developer build with -Werror

The group parameter is only used when cross-compiling, mark it as unused
otherwise. This is noticeable in the cmake branch because there we build
qmake with cmake and apply the same warning flags, as opposed to the
bootstrapped qmake build when using ... qmake.

The cache file parameter in qmake is unused and the
mustEnsureWritability is only used on Windows.

Change-Id: I08655d5150f5a967c2340ee7678bad3a4d69914f
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

qmake/generators/makefiledeps.cpp

@@ -246,7 +246,7 @@ bool QMakeSourceFileInfo::mocable(const QString &file)
     return false;
 }
 
-QMakeSourceFileInfo::QMakeSourceFileInfo(const QString &cf)
+QMakeSourceFileInfo::QMakeSourceFileInfo()
 {
     //dep_mode
     dep_mode = Recursive;

qmake/generators/makefiledeps.h

@@ -86,7 +86,7 @@ protected:
 
 public:
 
-    QMakeSourceFileInfo(const QString &cachefile="");
+    QMakeSourceFileInfo();
     virtual ~QMakeSourceFileInfo();
 
     QVector<QMakeLocalFileName> dependencyPaths() const { return depdirs; }

qmake/main.cpp

@@ -265,6 +265,8 @@ static bool copyFileTimes(QFile &targetFile, const QString &sourceFilePath,
                 return false;
         }
     }
+#else
+    Q_UNUSED(mustEnsureWritability);
 #endif
     if (!IoUtils::touchFile(targetFile.fileName(), sourceFilePath, errorString))
         return false;

src/corelib/global/qlibraryinfo.cpp

@@ -623,6 +623,8 @@ static const char *getPrefix(
 #  if QT_CONFIGURE_CROSSBUILD
     if (group == QLibraryInfo::DevicePaths)
         return QT_CONFIGURE_PREFIX_PATH;
+#  else
+    Q_UNUSED(group);
 #  endif
     static QByteArray extPrefixPath = getExtPrefixFromHostBinDir().toLatin1();
     return extPrefixPath.constData();