test: set dummy dir for CI cache

.github/actions/install_nim/action.yml

@@ -119,7 +119,7 @@ runs:
         cp ./scripts/build_nim.sh .
         env MAKE="${MAKE_CMD} -j${ncpu}" ARCH_OVERRIDE=${PLATFORM} NIM_COMMIT=${{ inputs.nim_branch }} \
           QUICK_AND_DIRTY_COMPILER=1 QUICK_AND_DIRTY_NIMBLE=1 CC=gcc \
-          bash build_nim.sh nim csources dist/my_nimble
+          bash build_nim.sh nim csources dist/my_nimble NONE
 #        nimble install nimble -y
 #        ls -la nim/bin
 #        rm -rf nim/bin/nimble.exe