fix image version issue for builder

docker-compose.yml

@@ -13,6 +13,7 @@ services:
       context: ./docker/sia
       dockerfile: Dockerfile
       args:
+        builder: alpine-1.5.0
         branch: master
     container_name: sia
     restart: unless-stopped
@@ -28,7 +29,7 @@ services:
       - 9980
 
   sia-upload:
-    image: nebulouslabs/sia:alpine-latest
+    image: nebulouslabs/sia:alpine-1.5.0
     container_name: sia-upload
     restart: unless-stopped
     environment:

docker/sia/Dockerfile

@@ -4,11 +4,11 @@ ENV GOOS linux
 ENV GOARCH amd64
 
 ARG branch=master
+ARG builder=latest
 
 RUN git clone https://gitlab.com/NebulousLabs/Sia.git --single-branch --branch ${branch}
 RUN make release --directory Sia
 
-FROM nebulouslabs/sia:alpine-latest
+FROM nebulouslabs/sia:${builder}
 
-COPY --from=sia-builder /go/bin/siac /sia/siac
-COPY --from=sia-builder /go/bin/siad /sia/siad
+COPY --from=sia-builder /go/bin/siac /go/bin/siad /usr/bin/