Copy trusted keys to chroot

If the user has installed additional sources (for example dbgsym
sources), and the trusted keys are not available in the chroot, the
updates in the chroot can fail as some keys aren't available.

scripts/install_pulseaudio_sources_apt_wrapper.sh

@@ -232,6 +232,15 @@ for file in $(find /etc/apt/ /etc/apt/sources.list.d/ /etc/apt/mirrors/ \
     sudo install -Dm 0644 $file $BUILDROOT/$file || exit $?
 done
 
+for file in $(find /etc/apt/trusted.gpg.d/ \
+    -maxdepth 1 \
+    -type f -name '*.gpg' ); do
+    if [ ! -f "$BUILDROOT/$file" ]; then
+        echo "- Copying $file to the root"
+        sudo install -Dm 0644 $file $BUILDROOT/$file || exit $?
+    fi
+done
+
 # Create a separate directory in $BUILDROOT to hold the build
 # artefacts.
 #