Android Toolchain: Remove unused member variable

Change-Id: I5029c6897298ef3f35079b6990dbbe4242789c42
Reviewed-by: BogDan Vatra <bog_dan_ro@yahoo.com>
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>

src/plugins/android/androidtoolchain.h

@@ -76,7 +76,6 @@ private:
     AndroidToolChain(const AndroidToolChain &);
 
     int m_qtVersionId;
-    mutable QString m_sysroot;
     friend class AndroidToolChainFactory;
 };