Add option for globally changing the base environment for tools

Fixes: QTCREATORBUG-22123
Change-Id: I00a5bbdf92e5dab513cb12f3518a2abb1adbb9cd
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

src/libs/utils/environment.cpp

@@ -313,6 +313,11 @@ void Environment::modifySystemEnvironment(const EnvironmentItems &list)
     staticSystemEnvironment->modify(list);
 }
 
+void Environment::setSystemEnvironment(const Environment &environment)
+{
+    *staticSystemEnvironment = environment;
+}
+
 /** Expand environment variables in a string.
  *
  * Environment variables are accepted in the following forms: