Build the release one target at a time so it fits in memory

The v0.2.0 plugin release ran for 31 minutes and then died:

    build failed: exit status 1:
      github.com/pulumi/pulumi/sdk/v3/go/pulumi:
      compile: signal: killed
    target=darwin_amd64_v1

`signal: killed` is the OOM killer. A bridged provider links the entire
Terraform provider and the Pulumi SDK into a single ~100MB binary, and
goreleaser defaults its parallelism to the CPU count, so several of those
compiles were resident at once on a runner that could not hold them.

Serialise the builds and lower the compiler's GC target. Slower in wall-clock,
but it is the difference between a release that finishes and one that does
not.

.gitea/workflows/release.yml

@@ -41,13 +41,23 @@ jobs:
           go-version: ${{ env.GO_VERSION }}
           cache: false
 
+      # A bridged Pulumi provider links the whole Terraform provider plus the
+      # Pulumi SDK into one ~100MB binary, and compiling that is memory-hungry.
+      # goreleaser defaults its parallelism to the CPU count, so several of
+      # those compiles overlap and the runner OOMs -- the v0.2.0 release died
+      # after 31 minutes with `compile: signal: killed` on darwin_amd64.
+      #
+      # Build one target at a time. It is slower in wall-clock but it is the
+      # difference between a release that finishes and one that does not.
+      # GOGC trades some CPU for a lower peak heap in the compiler itself.
       - uses: goreleaser/goreleaser-action@v6
         with:
           version: latest
-          args: release --clean
+          args: release --clean --parallelism 1
           workdir: pulumi-dokploy
         env:
           GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          GOGC: "50"
 
   sdks:
     needs: plugin