github: print catch2 location

.github/workflows/main-stock-ubuntu.yml

@@ -24,7 +24,10 @@ jobs:
       - name: Install catch2
         # install catch2.
         # see [[https://stackoverflow.com/questions/57982945/how-to-apt-get-install-in-a-github-actions-workflow]]
-        run: sudo apt-get install -y catch2
+        run: |
+          sudo apt-get install -y catch2
+          # where did it put the dang thing?
+          find / -name catch.hpp
 
       - name: bootstrap xo-cmake
         run: |