Remove unnecessary overloads of BuildConfiguration::baseEnvironment()

Change-Id: I9805f5cb87f6c30b7952f9970b007f883eb62507
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/cmakeprojectmanager/cmakebuildconfiguration.h

@@ -60,8 +60,6 @@ public:
 
     ProjectExplorer::IOutputParser *createOutputParser() const;
 
-    Utils::Environment baseEnvironment() const;
-
     BuildType buildType() const;
 
     bool useNinja() const;