Add GCC/C example.

Signed-off-by: Alex Ellis <alexellis2@gmail.com>

sample-functions/CHelloWorld/src/Dockerfile

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+FROM alpine:3.6 as builder
+RUN apk add --no-cache curl \
+    && curl -SL https://github.com/alexellis/faas/releases/download/0.6.4/fwatchdog > /usr/bin/fwatchdog \
+    && chmod +x /usr/bin/fwatchdog \
+    && apk --no-cache del curl
+
+WORKDIR /root/
+
+RUN apk add --no-cache gcc \
+                       musl-dev
+COPY main.c     .
+
+RUN gcc main.c -static -o /main \
+ && chmod +x /main \
+ && /main
+
+FROM scratch
+
+COPY --from=builder /main               /
+COPY --from=builder /usr/bin/fwatchdog  /
+COPY --from=builder /tmp /tmp
+
+ENV fprocess="/main"
+
+CMD ["/fwatchdog"]
+

sample-functions/CHelloWorld/src/main.c

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+#include<stdio.h>
+
+int main() {
+
+  printf("Hello world\n");
+
+  return 0;
+}
+