mockbuild: add a swapfile to el8 aarch64 builds

The pulp client is very large and defines a lot of symbols in on
package, which causes very large memory usage on el8 aarch64 (presumably
because of 64k page sizes).
Adding a 1 GiB swapfile fixes the issue in our CI runners.

schutzbot/mockbuild.sh

@@ -72,6 +72,14 @@ if [[ "$ID" == rhel ]] && sudo subscription-manager status; then
   DISTRO_VERSION=rhel-${VERSION_ID%.*}-cdn
 fi
 
+# EL8 aarch64 builds run out of memory and get killed. A swapfile fixes this.
+if [[ "$PLATFORM_ID" == "platform:el8" ]] && [[ "${ARCH}" == "aarch64" ]]; then
+    sudo dd if=/dev/zero of=/swapfile bs=1M count=1024
+    sudo chmod 600 /swapfile
+    sudo mkswap /swapfile
+    sudo swapon /swapfile
+fi
+
 # Relative path of the repository – used for constructing both the local and
 # remote paths below, so that they're consistent.
 REPO_PATH=osbuild-composer/${DISTRO_VERSION}/${ARCH}/${COMMIT}