Allow force-patching webpack.config.js when self-building Element

We were applying the low-memory system patch to webpack.config.js
on systems with < 4GB memory.

From now on, we also let people force-enable patching by toggling the
`matrix_client_element_container_image_self_build_low_memory_system_patch_enabled`
variable.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1357

roles/matrix-client-element/defaults/main.yml

@@ -2,6 +2,10 @@ matrix_client_element_enabled: true
 
 matrix_client_element_container_image_self_build: false
 matrix_client_element_container_image_self_build_repo: "https://github.com/vector-im/riot-web.git"
+# Controls whether to patch webpack.config.js when self-building, so that building can pass on low-memory systems (< 4 GB RAM):
+# - https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1357
+# - https://github.com/vector-im/element-web/issues/19544
+matrix_client_element_container_image_self_build_low_memory_system_patch_enabled: "{{ ansible_memtotal_mb < 4096 }}"
 
 matrix_client_element_version: v1.9.3
 matrix_client_element_docker_image: "{{ matrix_client_element_docker_image_name_prefix }}vectorim/element-web:{{ matrix_client_element_version }}"

roles/matrix-client-element/tasks/setup_install.yml

@@ -41,7 +41,7 @@
     owner: root
     group: root
     mode: '0644'
-  when: "matrix_client_element_container_image_self_build|bool and ansible_memtotal_mb < 4096"
+  when: "matrix_client_element_container_image_self_build|bool and matrix_client_element_container_image_self_build_low_memory_system_patch_enabled|bool"
 
 - name: Ensure Element Docker image is built
   docker_image: