Move RISCV env. var. setting interal to scripts

.github/actions/run-tests/action.yml

@@ -15,9 +15,6 @@ runs:
   steps:
     - name: run rtl build script cache of chipyard root should have been loaded by prepare-rtl
       run: |
-        export RISCV="$GITHUB_WORKSPACE/riscv-tools-install"
-        export LD_LIBRARY_PATH="$RISCV/lib"
-        export PATH="$RISCV/bin:$PATH"
         ./.github/scripts/${{ inputs.run-script }} ${{ inputs.project-key }}
       shell: bash