Consolidate ED dockerbuild into CD nx workflow (#32923)

* Consolidate ED dockerbuild into CD nx workflow

* Touch Dockerfile to convince CI to be happy

apps/desktop/dockerbuild/Dockerfile

@@ -1,5 +1,6 @@
 # Docker image to facilitate building Element Desktop's native bits using a glibc version (2.31)
 # with broader compatibility, down to Debian bullseye & Ubuntu focal.
+
 FROM rust:bullseye@sha256:16950191527a4cb9e0762d9d48b705a6315158e4035e64f7a93ce8656a1b053c
 
 ENV DEBIAN_FRONTEND=noninteractive

apps/desktop/project.json

@@ -0,0 +1,24 @@
+{
+    "$schema": "../../node_modules/nx/schemas/project-schema.json",
+    "projectType": "app",
+    "root": "apps/desktop",
+    "targets": {
+        "docker:build": {
+            "executor": "@nx-tools/nx-container:build",
+            "dependsOn": ["docker:prebuild"],
+            "options": {
+                "load": true,
+                "engine": "docker",
+                "platforms": ["linux/amd64", "linux/arm64"],
+                "provenance": "true",
+                "sbom": true,
+                "context": "apps/desktop",
+                "file": "apps/desktop/dockerbuild/Dockerfile",
+                "metadata": {
+                    "images": ["ghcr.io/element-hq/element-web/desktop-build-env"],
+                    "tags": ["type=ref,event=branch", "type=raw,enable={{is_default_branch}},value=$PLAYWRIGHT_VERSION"]
+                }
+            }
+        }
+    }
+}