stop side-effect of cd - at the end of these scripts

s/build

@@ -31,4 +31,4 @@ fi
 
 cd $ROOT/$BIN_DIR
 make $MAKEOPTS && make test
-cd -
+cd $OLDPWD

s/cmake-init

@@ -44,4 +44,4 @@ cmake .. \
  -DCMAKE_INCLUDE_PATH=$INCLUDE_PATH \
  -DCMAKE_PREFIX_PATH=$PREFIX_PATH \
  -DCMAKE_INSTALL_PREFIX=$HOME/eressea $*
-cd -
+cd $OLDPWD

s/install

@@ -16,4 +16,4 @@ BIN_DIR="build-$MACHINE-$CC-Debug"
 
 cd $ROOT/$BIN_DIR
 make install
-cd -
+cd $OLDPWD

s/runtests

@@ -18,4 +18,4 @@ fi
 $ROOT/$BIN_DIR/eressea/test_eressea
 cd $ROOT
 $ROOT/$BIN_DIR/eressea/eressea -v0 scripts/runtests.lua
-cd -
+cd $OLDWPD