Speedup build

.ci/dolphin/build-gamecube.sh

@@ -8,6 +8,6 @@ docker run -it -v ./:/workdir myapp:latest /bin/bash -c ' \
   # cmake -S. -Bbuild2 -DDUSK_TARGET_SYSTEM=gamecube -DCMAKE_TOOLCHAIN_FILE="$DEVKITPRO/cmake/GameCube.cmake" && \
   cmake -S. -Bbuild2 -DDUSK_TARGET_SYSTEM=wii -DCMAKE_TOOLCHAIN_FILE="$DEVKITPRO/cmake/Wii.cmake" && \
   cd build2 && \
-  make VERBOSE=1 && \
+  make -j$(nproc) VERBOSE=1 && \
   cp ./Dusk.dol ./boot.dol
 '