ci: run codecov outside docker

Dockerfile

@@ -1,21 +1,4 @@
 FROM golang:1.17.2 as build
-ARG CODECOV_ENV
-ARG CODECOV_TOKEN
-ARG CODECOV_URL
-ARG CODECOV_SLUG
-ARG VCS_COMMIT_ID
-ARG VCS_BRANCH_NAME
-ARG VCS_PULL_REQUEST
-ARG VCS_SLUG
-ARG VCS_TAG
-ARG CI_BUILD_URL
-ARG CI_BUILD_ID
-ARG CI_JOB_ID
-ARG GITLAB_CI
-ARG CI_BUILD_REF_NAME
-ARG CI_BUILD_ID
-ARG CI_BUILD_REPO
-ARG CI_BUILD_REF
 WORKDIR /build
 ENV CGO_ENABLED=0
 ADD . /build
@@ -27,10 +10,11 @@ RUN ["/bin/bash", "-c", "cat coverage.txt.tmp | grep -v -f <(find . -type f | xa
 RUN go tool cover -html=coverage.txt -o coverage.html
 RUN go tool cover -func=coverage.txt
 RUN rm coverage.txt.tmp
-RUN curl -s https://codecov.io/bash | bash
-
 RUN GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -mod=readonly -o release/cron-checker -ldflags '-w -s'
 
+FROM scratch as export
+COPY --from=build /build/coverage.txt /
+
 FROM scratch
 COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 COPY --from=build /build/release/cron-checker /