Add build documentation

BUILD.md

@@ -0,0 +1,43 @@
+# postgres-backup-local build instructions
+
+To build and push all images to it's own repository.
+
+## Prepare environment
+
+ * Configure you system to use [Docker Buildx](https://docs.docker.com/buildx/working-with-buildx/).
+ * Prepare crosscompile environment (see below).
+
+### Prepare crosscompile environment
+
+In order to work in Arch Linux the following initialization commands will be required:
+
+```sh
+docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
+docker buildx rm multibuilder
+docker buildx create --name multibuilder --platform linux/amd64,linux/arm64,linux/arm/v7 --driver docker-container --use
+docker buildx inspect --bootstrap
+```
+
+## Generate the images
+
+### Generate build configuration
+
+In order to modify the image name or any other configurable parameter run the `generate.sh` script.
+
+```sh
+IMAGE_NAME="prodrigestivill/postgres-backup-local" ./generate.sh config.hcl
+```
+
+### Build the images
+
+In order to only build the images locally run the following command:
+
+```sh
+docker buildx bake --pull -f config.hcl
+```
+
+In order to publish directly to the repository run this command instead:
+
+```sh
+docker buildx bake --pull --set common.output=type=registry -f config.hcl
+```