Update Dockerfile

Fix DLL load error

Docker/linux-arm32/Dockerfile

@@ -1,4 +1,4 @@
-FROM gcc:7 AS build-env
+FROM arm32v7/gcc:7 AS build-env
 WORKDIR /app
 
 # copy .c and .h file
@@ -17,4 +17,4 @@ WORKDIR /app
 COPY $EXE_DIR/ ./
 COPY --from=build-env /app/libcomWrapper.so /usr/lib/
 
-CMD ["/usr/bin/dotnet", "iot-edge-modbus.dll"]
+CMD ["/usr/bin/dotnet", "iot-edge-modbus.dll"]