Merge pull request #16 from discoverygarden/fix/build

ISX-71: Avoid `/tmp` directory.

Author: adamcbowman

Dockerfile

@@ -1,4 +1,12 @@
-FROM debian:12-slim
+ARG BUILD_DIR=/build
+ARG BASE_IMAGE=debian:12-slim
+
+FROM $BASE_IMAGE AS debsuryorg-key
+
+ARG BUILD_DIR
+ADD --link https://packages.sury.org/debsuryorg-archive-keyring.deb $BUILD_DIR/debsuryorg-archive-keyring.deb
+
+FROM $BASE_IMAGE
 
 ARG TARGETARCH
 ARG TARGETVARIANT
@@ -47,8 +55,10 @@ COPY clear-cache /bin/clear-cache
 
 # Use Dockerfile-native mechanisms for PHP repo setup
 # Procedure adapted from https://packages.sury.org/php/README.txt
-ADD --link https://packages.sury.org/debsuryorg-archive-keyring.deb /tmp/debsuryorg-archive-keyring.deb
-RUN dpkg -i /tmp/debsuryorg-archive-keyring.deb
+ARG BUILD_DIR
+RUN \
+  --mount=type=bind,target=$BUILD_DIR,source=$BUILD_DIR,from=debsuryorg-key \
+  dpkg -i $BUILD_DIR/debsuryorg-archive-keyring.deb
 RUN \
   --mount=type=cache,target=/var/lib/apt/lists,sharing=locked,id=debian-apt-lists-$TARGETARCH$TARGETVARIANT \
   --mount=type=cache,target=/var/cache/apt/archives,sharing=locked,id=debian-apt-archives-$TARGETARCH$TARGETVARIANT \