build: persist Go build cache across Docker release builds

Mount .gocache/ from the host into the builder container so --rm
container removal no longer wipes GOCACHE between runs.

.gitignore

@@ -1,6 +1,9 @@
 # Build outputs
 dist/
 
+# Persistent Go build cache for Docker-based release builds.
+.gocache/
+
 # Generated Windows resource compiled from packaging/windows/gosentry.rc.
 cmd/gosentry/*.syso
 

scripts/build-linux-docker.sh

@@ -18,12 +18,14 @@ fi
 docker build -f Dockerfile -t "$tag" .
 
 mkdir -p "$(dirname "$output")"
+mkdir -p "$(pwd)/.gocache"
 docker run --rm \
     "${docker_user_args[@]}" \
     -e "VERSION=${version}" \
     -e "OUTPUT=${output}" \
     -e "GOCACHE=/tmp/go-build-cache" \
     -v "$(pwd):/src" \
+    -v "$(pwd)/.gocache:/tmp/go-build-cache" \
     -w /src \
     "$tag" \
     bash -c 'CGO_ENABLED=1 GOOS=linux GOARCH=amd64 go build -buildvcs=false -trimpath -ldflags "-s -w -X gitea.mixdep.ru/mix/gosentry/src/app.Version=${VERSION}" -o "${OUTPUT}" ./cmd/gosentry'

scripts/build-release-linux.sh

@@ -88,11 +88,13 @@ normalize_targets() {
 }
 
 run_in_builder() {
+    mkdir -p "${repo_root}/.gocache"
     docker run --rm \
         "${docker_user_args[@]}" \
         -e "VERSION=${version}" \
         -e "GOCACHE=/tmp/go-build-cache" \
         -v "${repo_root}:/src" \
+        -v "${repo_root}/.gocache:/tmp/go-build-cache" \
         -w /src \
         "$tag" \
         bash -c "$1"