chore: decrease make build-simapp-docker time

[rootulp]

Closes #60

Testing

Now it takes less time to create the Docker image and 9GB isn't copied over.

$ make build-simapp-docker
--> Updating go.mod
--> Building Docker image
/opt/homebrew/bin/docker build -t ghcr.io/celestiaorg/simapp -f docker/Dockerfile .
[+] Building 88.6s (15/15) FINISHED
 => [internal] load build definition from Dockerfile                                                                                                                                                         3.7s
 => => transferring dockerfile: 1.39kB                                                                                                                                                                       0.0s
 => [internal] load metadata for docker.io/library/alpine:3.20                                                                                                                                               0.4s
 => [internal] load metadata for docker.io/library/golang:1.23.1-alpine3.20                                                                                                                                  0.4s
 => [internal] load .dockerignore                                                                                                                                                                            0.0s
 => => transferring context: 65B                                                                                                                                                                             0.0s
 => [builder 1/5] FROM docker.io/library/golang:1.23.1-alpine3.20@sha256:ac67716dd016429be8d4c2c53a248d7bcdf06d34127d3dc451bda6aa5a87bc06                                                                    0.0s
 => [internal] load build context                                                                                                                                                                            3.3s
 => => transferring context: 4.27MB                                                                                                                                                                          3.2s
 => [stage-1 1/4] FROM docker.io/library/alpine:3.20@sha256:1e42bbe2508154c9126d48c2b8a75420c3544343bf86fd041fb7527e017a4b4a                                                                                 0.0s
 => CACHED [builder 2/5] RUN apk update && apk add --no-cache     gcc     git     linux-headers     make     musl-dev                                                                                        0.0s
 => [builder 3/5] COPY . /celestia_zkevm_ibc_demo                                                                                                                                                           19.9s
 => [builder 4/5] WORKDIR /celestia_zkevm_ibc_demo                                                                                                                                                           0.0s
 => [builder 5/5] RUN uname -a &&    CGO_ENABLED=0 GOOS=linux GOARCH=arm64     make build-simapp                                                                                                            61.1s
 => CACHED [stage-1 2/4] RUN apk update && apk add --no-cache     bash     curl     jq     make     && adduser celestia     -D     -g celestia     -h /home/celestia     -s /sbin/nologin     -u 10001       0.0s
 => CACHED [stage-1 3/4] COPY --from=builder /celestia_zkevm_ibc_demo/build/simd /bin/simd                                                                                                                   0.0s
 => CACHED [stage-1 4/4] WORKDIR /home/celestia                                                                                                                                                              0.0s
 => exporting to image                                                                                                                                                                                       0.0s
 => => exporting layers                                                                                                                                                                                      0.0s
 => => writing image sha256:38b6d542be9754c39335dd409fee96d334cd15a3a928a790bd1f4f6a0c6bfb90                                                                                                                 0.0s
 => => naming to ghcr.io/celestiaorg/simapp:latest