Adding curl to a couple of linux distros that were missing it.

scripts/docker/alpine.3.6/Dockerfile

@@ -6,6 +6,8 @@
 # Dockerfile that creates a container suitable to build dotnet-cli
 FROM microsoft/dotnet-buildtools-prereqs:alpine-3.6-3148f11-20171119021156
 
+RUN apk update && apk upgrade && apk add --no-cache curl ncurses
+
 # This Dockerfile doesn't use the USER_ID, but the parameter needs to be declared to prevent docker
 # from issuing a warning
 ARG USER_ID=0

scripts/docker/ubuntu.18.04/Dockerfile

@@ -8,6 +8,8 @@ FROM microsoft/dotnet-buildtools-prereqs:ubuntu-18.04-f90bc20-20180320154721
 
 RUN apt-get update && \
     apt-get -qqy install \
+        curl \
+        libcurl4 \
         sudo && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*