GHA CI: put libtorrent into its own directory

Previously it was rooted within qbt project and it caused some issues when running
'update translations' command.

.github/workflows/ci_ubuntu.yaml

@@ -25,6 +25,7 @@ jobs:
     env:
       boost_path: "${{ github.workspace }}/../boost"
       harden_flags: "-D_FORTIFY_SOURCE=2 -D_GLIBCXX_ASSERTIONS"
+      libtorrent_path: "${{ github.workspace }}/../libtorrent"
 
     steps:
       - name: Checkout repository
@@ -67,8 +68,9 @@ jobs:
             --branch v${{ matrix.libt_version }} \
             --depth 1 \
             --recurse-submodules \
-            https://github.com/arvidn/libtorrent.git
-          cd libtorrent
+            https://github.com/arvidn/libtorrent.git \
+            ${{ env.libtorrent_path }}
+          cd ${{ env.libtorrent_path }}
           CXXFLAGS="$CXXFLAGS ${{ env.harden_flags }}" \
           cmake \
             -B build \
@@ -120,7 +122,7 @@ jobs:
           mkdir upload/cmake
           cp build/compile_commands.json upload/cmake
           mkdir upload/cmake/libtorrent
-          cp libtorrent/build/compile_commands.json upload/cmake/libtorrent
+          cp ${{ env.libtorrent_path }}/build/compile_commands.json upload/cmake/libtorrent
 
       - name: Install AppImage
         run: |