Adding protobuf layer

layers/protobuf/Dockerfile

@@ -0,0 +1,15 @@
+ARG PHP_VERSION
+ARG BREF_VERSION
+FROM bref/build-php-$PHP_VERSION:$BREF_VERSION AS ext
+
+RUN MAKEFLAGS="-j $(nproc)" pecl install protobuf > /dev/null
+RUN cp `php-config --extension-dir`/protobuf.so /tmp/protobuf.so
+RUN strip --strip-debug /tmp/protobuf.so
+RUN echo 'extension=protobuf.so' > /tmp/ext.ini
+
+# Build the final image with just the files we need
+FROM scratch
+
+# Copy things we installed to the final image
+COPY --from=ext /tmp/protobuf.so /opt/bref/extensions/protobuf.so
+COPY --from=ext /tmp/ext.ini /opt/bref/etc/php/conf.d/ext-protobuf.ini

layers/protobuf/config.json

@@ -0,0 +1,8 @@
+{
+    "php": [
+        "81",
+        "82",
+        "83",
+        "84"
+    ]
+}

layers/protobuf/test.php

@@ -0,0 +1,8 @@
+<?php
+
+if (!class_exists($function = \Google\Protobuf\Any::class)) {
+    echo sprintf('FAIL: Class "%s" does not exist.', $function) . PHP_EOL;
+    exit(1);
+}
+
+exit(0);