Improved install test

Author: ankane

.github/workflows/build.yml

@@ -32,4 +32,7 @@ jobs:
           sudo apt-get install valgrind
           valgrind --leak-check=yes build/test
 
+      # test install
+      - run: cmake -S . -B build
+      - run: cmake --build build
       - run: sudo cmake --install build