Build soh.o2r in CI without libultraship or soh

SOH_TOOLS_ONLY returns from the root CMakeLists once the asset tools are
declared, before libultraship and soh are added, so a configure that only
needs soh-o2r-packer never reaches LUS's find_package(SDL2 REQUIRED).

That lets generate-soh-otr drop building SDL2 from source, SDL2_net, and
the deps cache that existed to hold the SDL2 tarball -- eleven steps down
to six. Verified a tools-only build produces the archive with all 1,042
entries matching.

The tool targets move above the sub-projects so the early return can sit
between them; they only ever needed torch. The packer creates its output
directory, which previously came for free from soh's build directory.

.github/workflows/generate-builds.yml

@@ -26,40 +26,13 @@ jobs:
       run: |
         sudo apt-get update
         sudo apt-get install -y $(cat linux-build-deps/apt.txt)
-    - name: Restore Cached deps folder
-      uses: actions/cache/restore@v5
-      with:
-        key: ${{ runner.os }}-deps-${{ github.ref }}-${{ github.sha }}
-        restore-keys: |
-          ${{ runner.os }}-deps-${{ github.ref }}-
-          ${{ runner.os }}-deps-
-        path: deps
-    - name: Create deps folder
-      run: mkdir -p deps
     - name: Add ccache to PATH
       run: |
         echo "/usr/lib/ccache" >> "$GITHUB_PATH"
         echo "/usr/local/opt/ccache/libexec" >> "$GITHUB_PATH"
-    - name: Install latest SDL
-      run: |
-        if [ ! -d "deps/SDL2-2.30.3" ]; then
-          wget https://github.com/libsdl-org/SDL/releases/download/release-2.30.3/SDL2-2.30.3.tar.gz
-          tar -xzf SDL2-2.30.3.tar.gz -C deps
-        fi
-        cd deps/SDL2-2.30.3
-        ./configure --enable-hidapi-libusb
-        make -j 10
-        sudo make install
-        sudo cp -av /usr/local/lib/libSDL* /lib/x86_64-linux-gnu/
-    - uses: ./.github/actions/install-sdl2-net
-    - name: Copy SDL libs to multiarch dir
-      run: sudo cp -av /usr/local/lib/libSDL* /lib/x86_64-linux-gnu/
-    - name: Remove distro tinyxml2
-      run: sudo apt-get remove libtinyxml2-dev
-    - uses: ./.github/actions/install-tinyxml2
     - name: Generate soh.o2r
       run: |
-        cmake --no-warn-unused-cli -H. -Bbuild-cmake -GNinja -DCMAKE_BUILD_TYPE:STRING=Release
+        cmake --no-warn-unused-cli -H. -Bbuild-cmake -GNinja -DCMAKE_BUILD_TYPE:STRING=Release -DSOH_TOOLS_ONLY=ON
         cmake --build build-cmake --config Release --target GenerateSohOtr -j3
     - name: Upload soh.o2r
       uses: actions/upload-artifact@v7