update to build appropriately

Dockerfile

@@ -2,25 +2,31 @@ FROM golang:alpine AS lib_builder
 
 WORKDIR /foundry
 
-RUN apk add git make linux-headers cmake g++
+# install build deps (use build-base to get gcc/g++)
+RUN apk add --no-cache git build-base linux-headers cmake
 RUN git clone https://github.com/jgarff/rpi_ws281x.git \
-  && cd rpi_ws281x \ 
+  && cd rpi_ws281x \
   && mkdir build \
-  && cd build \ 
+  && cd build \
   && cmake -D BUILD_SHARED=OFF -D BUILD_TEST=OFF .. \
-  && cmake --build . \
-  && make install
+  && cmake --build . --target install
 
 # Stage 1 : Build a go image with the rpi_ws281x C library and the go wrapper
 
+
 FROM golang:alpine
 COPY --from=lib_builder /usr/local/lib/libws2811.a /usr/local/lib/
 COPY --from=lib_builder /usr/local/include/ws2811 /usr/local/include/ws2811
-RUN apk add git make linux-headers cmake g++
+
+# enable cgo and install build deps for the Go build
+ENV CGO_ENABLED=1
+RUN apk add --no-cache git build-base linux-headers cmake
+
 WORKDIR /go/src/github.com/rpi-ws281x/rpi-ws281x-go
 COPY . .
-RUN GO111MODULE=off go get -d -v ./...
-RUN GO111MODULE=off go build -v ./...
+# Build in GOPATH mode (this repo has no go.mod).
+ENV GO111MODULE=off
+RUN go build -v ./...
 
 WORKDIR /go