[GHA] delete build files etc

In case we run out of space on the runner

.github/workflows/build-test.yml

@@ -259,8 +259,10 @@ jobs:
 
           # Install ROOT (warning: currently only valid on Ubuntu)
           if test "${{matrix.ROOT}}XX" == "ONXX"; then
-             wget https://root.cern/download/root_v6.28.12.Linux-ubuntu20-x86_64-gcc9.4.tar.gz
-             tar -xzvf root_v6.28.12.Linux-ubuntu20-x86_64-gcc9.4.tar.gz
+             ROOT_file=root_v6.28.12.Linux-ubuntu20-x86_64-gcc9.4.tar.gz
+             wget https://root.cern/download/"$ROOT_file"
+             tar -xzvf "$ROOT_file"
+             rm "$ROOT_file"
              source root/bin/thisroot.sh
           fi
 
@@ -360,6 +362,43 @@ jobs:
           # execute tests
           ctest --output-on-failure -C ${BUILD_TYPE} ${EXCLUDE}
 
+    - name: examples
+      shell: bash
+      run: |
+          set -ex;
+          PATH=${CMAKE_INSTALL_PREFIX}/bin:$PATH
+          # Run examples to see if they work
+          cd ${GITHUB_WORKSPACE}/examples/PET_simulation
+          ./run_simulation.sh 1> /dev/null
+
+          # Run the Demo executables
+          EXE_LOC=${GITHUB_WORKSPACE}/build/src/examples/C++/using_STIR_LOCAL
+          cd ${GITHUB_WORKSPACE}/examples/C++/using_STIR_LOCAL
+
+          generate_image generate_image.par
+          forward_project sino.hs image.hv  small.hs
+
+          # Cannot test demo1 or demo2 as they require interactivity. Piping does not work.
+          ${EXE_LOC}/demo3 demo.par --display_off
+          ${EXE_LOC}/demo3 demoPM.par --display_off
+          ${EXE_LOC}/demo4_obj_fun demo4_obj_fun.par
+          ${EXE_LOC}/demo5_line_search demo5_line_search.par
+
+          # build and run C++/using_installed_STIR
+          cd ${GITHUB_WORKSPACE}/examples/C++/using_installed_STIR
+          cmake -S . -B build/  -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_INSTALL_PREFIX}
+          cmake --build build/ --config Release  --target install
+          # run demo
+          demo_create_image
+          # just check if its output makes sense
+          list_image_info test.hv
+
+    - name: remove build
+      shell: bash
+         # remove to create some disk space
+      run:
+          rm -rf cd ${GITHUB_WORKSPACE}/build
+
     - name: recon_test_pack
       shell: bash
       env:
@@ -384,7 +423,7 @@ jobs:
             ./run_SPECT_tests.sh
           fi
 
-    - name: Upload log files for debugging
+    - name: Upload recon_test_pack log files for debugging
       uses: actions/upload-artifact@v3
       if: failure()
       with:
@@ -394,37 +433,6 @@ jobs:
           ${{ github.workspace }}/recon_test_pack/**/my_*s
         retention-days: 7
 
-    - name: examples
-      shell: bash
-      run: |
-          set -ex;
-          PATH=${CMAKE_INSTALL_PREFIX}/bin:$PATH
-          # Run examples to see if they work
-          cd ${GITHUB_WORKSPACE}/examples/PET_simulation
-          ./run_simulation.sh 1> /dev/null
-
-          # Run the Demo executables
-          EXE_LOC=${GITHUB_WORKSPACE}/build/src/examples/C++/using_STIR_LOCAL
-          cd ${GITHUB_WORKSPACE}/examples/C++/using_STIR_LOCAL
-
-          generate_image generate_image.par
-          forward_project sino.hs image.hv  small.hs
-
-          # Cannot test demo1 or demo2 as they require interactivity. Piping does not work.
-          ${EXE_LOC}/demo3 demo.par --display_off
-          ${EXE_LOC}/demo3 demoPM.par --display_off
-          ${EXE_LOC}/demo4_obj_fun demo4_obj_fun.par
-          ${EXE_LOC}/demo5_line_search demo5_line_search.par
-
-          # build and run C++/using_installed_STIR
-          cd ${GITHUB_WORKSPACE}/examples/C++/using_installed_STIR
-          cmake -S . -B build/  -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_INSTALL_PREFIX}
-          cmake --build build/ --config Release  --target install
-          # run demo
-          demo_create_image
-          # just check if its output makes sense
-          list_image_info test.hv
-
     - name: Python
       shell: bash
       run: |