Correct CI script, correct ICU testing config.

.github/workflows/ci.yml

@@ -88,7 +88,7 @@ jobs:
         run: sudo apt install g++-9 g++-10
       - name: Test
         run: ${{ matrix.compiler }} -std=${{ matrix.standard }}  -I../../include *.cpp ../../src/*.cpp -o regress -licuuc -licudata -licu18n && ./regress
-        working-directory: $GITHUB_WORKSPACE/test/regress
+        working-directory: ./test/regress
   ubuntu-bionic:
     runs-on: ubuntu-18.04
     strategy: