Changed image to golang:1.15-alpine

Signed-off-by: AdamKorcz <[email protected]>

hack/dockerfiles/fuzz.Dockerfile

@@ -1,17 +1,16 @@
-FROM ubuntu:20.04
-ENV DEBIAN_FRONTEND=noninteractive 
-RUN apt-get update && apt-get upgrade -y
-RUN apt-get install wget git software-properties-common build-essential -y
-RUN wget https://golang.org/dl/go1.14.9.linux-amd64.tar.gz
-RUN tar -xvf go1.14.9.linux-amd64.tar.gz
-RUN mv go /usr/local
+FROM golang:1.15-alpine
+ENV DEBIAN_FRONTEND=noninteractive
 
 RUN mkdir /root/src
 ENV GOPATH /root/go
 ENV GOROOT /usr/local/go
 ENV PATH $PATH:/usr/local/go/bin
 
-RUN go get github.com/moby/buildkit
-RUN go get -u github.com/dvyukov/go-fuzz/go-fuzz github.com/dvyukov/go-fuzz/go-fuzz-build
+RUN apk add --no-cache git mercurial \
+    && go get -u github.com/dvyukov/go-fuzz/go-fuzz \
+    github.com/dvyukov/go-fuzz/go-fuzz-build \
+    github.com/moby/buildkit \
+    && apk del git mercurial
 COPY fuzz.go /go/src/github.com/moby/buildkit/frontend/dockerfiles/parser/
-RUN cd /go/src/github.com/moby/buildkit/frontend/dockerfiles/parser && $GOPATH/bin/go-fuzz-build && $GOPATH/bin/go-fuzz
+RUN cd /go/src/github.com/moby/buildkit/frontend/dockerfiles/parser \
+    && $GOPATH/bin/go-fuzz-build && $GOPATH/bin/go-fuzz