Enabled unity build by default

Dockerfile-build-arch

@@ -12,6 +12,7 @@ ARG BUILD_PACKAGES="\
 	libconfig \
 	make \
 	pkgconfig \
+	stb \
 	taglib \
 	wt \
 	xxhash"
@@ -27,6 +28,7 @@ WORKDIR /tmp/lms/build
 
 ARG LMS_BUILD_TYPE=Release
 ARG LMS_UNITY_BUILD=ON
-RUN cmake .. -DCMAKE_BUILD_TYPE=${LMS_BUILD_TYPE} -DCMAKE_UNITY_BUILD=${LMS_UNITY_BUILD} -DLMS_IMAGE_BACKEND=graphicsmagick -DBUILD_BENCHMARKS=ON
+ARG LMS_IMAGE_BACKEND=stb
+RUN cmake .. -DCMAKE_BUILD_TYPE=${LMS_BUILD_TYPE} -DCMAKE_UNITY_BUILD=${LMS_UNITY_BUILD} -DLMS_IMAGE_BACKEND=${LMS_IMAGE_BACKEND} -DBUILD_BENCHMARKS=ON
 RUN VERBOSE=1 make -j$(nproc)
 RUN make test