Make comparison operators const

Reviewed-by: thorbjorn

src/plugins/projectexplorer/environment.cpp

@@ -288,12 +288,12 @@ void Environment::modify(const QList<EnvironmentItem> & list)
     *this = resultEnvironment;
 }
 
-bool Environment::operator!=(const Environment &other)
+bool Environment::operator!=(const Environment &other) const
 {
     return !(*this == other);
 }
 
-bool Environment::operator==(const Environment &other)
+bool Environment::operator==(const Environment &other) const
 {
     return m_values == other.m_values;
 }

src/plugins/projectexplorer/environment.h

@@ -94,8 +94,8 @@ public:
     static QStringList parseCombinedArgString(const QString &program);
     static QString joinArgumentList(const QStringList &arguments);
 
-    bool operator!=(const Environment &other);
-    bool operator==(const Environment &other);
+    bool operator!=(const Environment &other) const;
+    bool operator==(const Environment &other) const;
 private:
     QMap<QString, QString> m_values;
 };