Update Dockerfiles to use Alpine 3.16 for PHP test and extension images

- Changed base image from Alpine 3.21 to Alpine 3.16 in Dockerfiles for PHP test images (NTS and ZTS modes) and extension images (NTS and ZTS modes).
- Updated the Dockerfile for building Alpine libs toolchain images to also use Alpine 3.16.

Author: tudor-timcu

.github/workflows/Dockerfile.alpine-php-test-nts

@@ -5,7 +5,7 @@
 ARG PHP_VERSION=8.3
 ARG PHP_SRC_REF=PHP-${PHP_VERSION}
 
-FROM alpine:3.21 AS base
+FROM alpine:3.16 AS base
 SHELL ["/bin/ash", "-eo", "pipefail", "-c"]
 
 ENV TZ=Etc/UTC \

.github/workflows/Dockerfile.alpine-php-test-zts

@@ -5,7 +5,7 @@
 ARG PHP_VERSION=8.3
 ARG PHP_SRC_REF=PHP-${PHP_VERSION}
 
-FROM alpine:3.21 AS base
+FROM alpine:3.16 AS base
 SHELL ["/bin/ash", "-eo", "pipefail", "-c"]
 
 ENV TZ=Etc/UTC \

.github/workflows/Dockerfile.build-extension-alpine-nts

@@ -5,7 +5,7 @@
 ARG PHP_VERSION=8.3
 ARG PHP_SRC_REF=PHP-${PHP_VERSION}
 
-FROM alpine:3.21 AS base
+FROM alpine:3.16 AS base
 SHELL ["/bin/ash", "-eo", "pipefail", "-c"]
 
 ENV TZ=Etc/UTC \

.github/workflows/Dockerfile.build-extension-alpine-zts

@@ -5,7 +5,7 @@
 ARG PHP_VERSION=8.3
 ARG PHP_SRC_REF=PHP-${PHP_VERSION}
 
-FROM alpine:3.21 AS base
+FROM alpine:3.16 AS base
 SHELL ["/bin/ash", "-eo", "pipefail", "-c"]
 
 ENV TZ=Etc/UTC \

.github/workflows/Dockerfile.build-libs-alpine

@@ -1,6 +1,6 @@
 # Alpine-based image for building Go shared libraries with custom Go fork
 # that supports c-shared buildmode on musl-based systems.
-FROM alpine:3.21
+FROM alpine:3.16
 
 ARG GO_RELEASE_TAG=devel-go1.27-tlsdesc.1