ci: C++ builds on Ubuntu for Homebrew GCC and Clang

Author: nikobockerman

.github/CMakeUserPresets.json

@@ -14,6 +14,8 @@ runs:
       with:
         cache_packages: true
 
-    - name: Prepare CMakeUserPresets.json
-      run: cp .github/CMakeUserPresets.json solvers/cpp/CMakeUserPresets.json
+    - name: Prepare files
+      run: |
+        cp .github/files/CMakeUserPresets.json solvers/cpp/
+        cp .github/files/conan-profile-gcc-libstd++-for-clang solvers/cpp/
       shell: bash

.github/actions/cmake-project-setup/action.yaml

@@ -6,7 +6,7 @@ inputs:
     description: "Mode of operation regarding cache: 'prepare' or 'use'"
     required: false
   packages-hash-to-use:
-    description: "In 'use' mode, the hash of the package listing to use. From "
+    description: "In 'use' mode, the hash of the package listing to use. From output of an earlier 'prepare' mode run"
     required: false
 outputs:
   packages-hash: