Try to fix apt error.

builder/build.sh

@@ -20,8 +20,9 @@ EOF
 			PACKAGES="$(sed -f "${SCRIPT_DIR}/remove-comments.sed" < "${i}-packages-nr")"
 			if [ -n "$PACKAGES" ]; then
 				on_chroot << EOF
-apt-get -o APT::Acquire::Retries=3 --fix-missing install --no-install-recommends -y $PACKAGES
-apt-get -o APT::Acquire::Retries=3 --fix-missing install --no-install-recommends -y $PACKAGES
+apt-get -o APT::Acquire::Retries=3 --ignore-missing --fix-missing install --no-install-recommends -y $PACKAGES
+apt-get -o APT::Acquire::Retries=3 --ignore-missing --fix-missing install --no-install-recommends -y $PACKAGES
+apt-get -o APT::Acquire::Retries=3 --ignore-missing --fix-missing install --no-install-recommends -y $PACKAGES
 EOF
 			fi
 			log "End ${SUB_STAGE_DIR}/${i}-packages-nr"
@@ -31,8 +32,9 @@ EOF
 			PACKAGES="$(sed -f "${SCRIPT_DIR}/remove-comments.sed" < "${i}-packages")"
 			if [ -n "$PACKAGES" ]; then
 				on_chroot << EOF
-apt-get -o APT::Acquire::Retries=3 --fix-missing install -y $PACKAGES
-apt-get -o APT::Acquire::Retries=3 --fix-missing install -y $PACKAGES
+apt-get -o APT::Acquire::Retries=3 --ignore-missing --fix-missing install -y $PACKAGES
+apt-get -o APT::Acquire::Retries=3 --ignore-missing --fix-missing install -y $PACKAGES
+apt-get -o APT::Acquire::Retries=3 --ignore-missing --fix-missing install -y $PACKAGES
 EOF
 			fi
 			log "End ${SUB_STAGE_DIR}/${i}-packages"

builder/stage0/00-configure-apt/files/sources.list

@@ -1,3 +1,3 @@
-deb http://raspbian.raspberrypi.org/raspbian/ buster main contrib non-free rpi
+deb http://mirrors.ocf.berkeley.edu/raspbian/raspbian buster main contrib non-free rpi
 # Uncomment line below then 'apt-get update' to enable 'apt-get source'
 #deb-src http://raspbian.raspberrypi.org/raspbian/ buster main contrib non-free rpi