Minor fixes

This is just to fix a couple of minor annonyances:

• Geant4 can be build with Ninja now, so no reason to disable it
• we can build without setting $CMTCONFIG so relying on it is a bad idea
• somebody had the clever idea of adding git to the LCG stack, breaking the compilation in dev3/4, so I had to filter it away

/cc @kreps @adavis @gcorti

Geant4/G4config/CMakeLists.txt

@@ -57,7 +57,7 @@ ExternalProject_Add(Geant4
               -DGEANT4_USE_NETWORKVRML=ON
               -DGEANT4_USE_NETWORKDAWN=ON
               -DGEANT4_USE_INVENTOR=OFF
-              -DCMAKE_INSTALL_PREFIX=${CMAKE_SOURCE_DIR}/InstallArea/$ENV{CMTCONFIG}
+              -DCMAKE_INSTALL_PREFIX=${CMAKE_SOURCE_DIR}/InstallArea/${BINARY_TAG}
               -DCMAKE_INSTALL_LIBDIR=lib
               -DGEANT4_INSTALL_DATADIR=${G4DATA}
               -DGEANT4_BUILD_VERBOSE_CODE=${G4VERBOSE}