buildserver: switch to debian.sources

Since trixie debian.sources is recommended instead of sources.list. See

    https://wiki.debian.org/SourcesList

Fixes the following warning on apt-get update:

    W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list.d/debian.sources:1
    W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list.d/debian.sources:1
    W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:3 and /etc/apt/sources.list.d/debian.sources:1
    W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:3 and /etc/apt/sources.list.d/debian.sources:1

buildserver/provision-apt-get-install

@@ -38,12 +38,19 @@ if echo $debian_mirror | grep '^https' 2>&1 > /dev/null; then
     apt-get install ca-certificates
 fi
 
-cat << EOF > /etc/apt/sources.list
-deb ${debian_mirror} trixie main
-deb https://security.debian.org/debian-security trixie-security main
-deb ${debian_mirror} trixie-updates main
+cat << EOF > /etc/apt/sources.list.d/debian.sources
+Types: deb
+URIs: ${debian_mirror}
+Suites: trixie trixie-updates trixie-backports
+Components: main
+Signed-By: /usr/share/keyrings/debian-archive-keyring.pgp
+
+Types: deb
+URIs: https://security.debian.org/debian-security
+Suites: trixie-security
+Components: main
+Signed-By: /usr/share/keyrings/debian-archive-keyring.pgp
 EOF
-echo "deb ${debian_mirror} trixie-backports main" > /etc/apt/sources.list.d/backports.list
 
 apt-get update || apt-get update