You should build it from source code
FROM php:8.2-fpm-alpine AS ext-apcu
ENV EXT_APCU_VERSION=master
RUN curl -vvv https://github.com/krakjoe/apcu.git
RUN docker-php-source extract \
&& apk -Uu add git \
&& git clone --branch $EXT_APCU_VERSION --depth 1 https://github.com/krakjoe/apcu.git /usr/src/
