ci: Update docker images for arm

See https://github.com/cross-rs/cross/wiki/Configuration#builddockerfile
for context regarding the $CROSS_BASE_IMAGE environment variable. Here, it
resolves to
ghcr.io/cross-rs/armv7-unknown-linux-gnueabihf:{{cross_version}}

Relies on docker caching instead of pre-building the image.

Cross made the change to the GHCR on cross-rs/cross#609

Add newline at EOF for some files.

.github/workflows/cpal.yml

@@ -85,9 +85,6 @@ jobs:
         with:
           target: armv7-unknown-linux-gnueabihf
 
-      - name: Build image
-        run: docker build -t cross/cpal_armv7:v1 ./
-
       - name: Install cross
         run: cargo install cross
 

Cross.toml

@@ -1,7 +1,7 @@
 [target.armv7-unknown-linux-gnueabihf]
-image = "cross/cpal_armv7:v1"
+dockerfile = "Dockerfile"
 
 [target.armv7-unknown-linux-gnueabihf.env]
 passthrough = [
     "RUSTFLAGS",
-]
+]

Dockerfile

@@ -1,9 +1,10 @@
-FROM rustembedded/cross:armv7-unknown-linux-gnueabihf
+ARG CROSS_BASE_IMAGE
+FROM $CROSS_BASE_IMAGE
 
 ENV PKG_CONFIG_ALLOW_CROSS 1
 ENV PKG_CONFIG_PATH /usr/lib/arm-linux-gnueabihf/pkgconfig/
 
 RUN dpkg --add-architecture armhf && \
     apt-get update && \
     apt-get install libasound2-dev:armhf -y && \
-    apt-get install libjack-jackd2-dev:armhf libjack-jackd2-0:armhf -y \
+    apt-get install libjack-jackd2-dev:armhf libjack-jackd2-0:armhf -y \