Update Dockerfile

fix imagick 3.7.0 build

Dockerfile

@@ -49,7 +49,22 @@ RUN set -eux; \
     \
     # Install PHP extensions
     docker-php-ext-install ${PHP_EXTS}; \
-    pecl install imagick; \
+    #pecl install imagick; \
+# WARNING: imagick is likely not supported on Alpine: https://github.com/Imagick/imagick/issues/328
+# https://pecl.php.net/package/imagick
+# https://github.com/Imagick/imagick/commit/5ae2ecf20a1157073bad0170106ad0cf74e01cb6 (causes a lot of build failures, but strangely only intermittent ones)
+# see also https://github.com/Imagick/imagick/pull/641
+# this is "pecl install imagick-3.7.0", but by hand so we can apply a small hack / part of the above commit
+# Thanks to @tianon https://github.com/docker-library/wordpress/commit/509adb58cbc7463a03e317931df65868ec8a3e92
+    curl -fL -o imagick.tgz 'https://pecl.php.net/get/imagick-3.7.0.tgz'; \
+    echo '5a364354109029d224bcbb2e82e15b248be9b641227f45e63425c06531792d3e *imagick.tgz' | sha256sum -c -; \
+    tar --extract --directory /tmp --file imagick.tgz imagick-3.7.0; \
+    grep '^//#endif$' /tmp/imagick-3.7.0/Imagick.stub.php; \
+    test "$(grep -c '^//#endif$' /tmp/imagick-3.7.0/Imagick.stub.php)" = '1'; \
+    sed -i -e 's!^//#endif$!#endif!' /tmp/imagick-3.7.0/Imagick.stub.php; \
+    grep '^//#endif$' /tmp/imagick-3.7.0/Imagick.stub.php && exit 1 || :; \
+    docker-php-ext-install /tmp/imagick-3.7.0; \
+    rm -rf imagick.tgz /tmp/imagick-3.7.0; \    
     docker-php-ext-enable imagick; \
     \
     # Cleanup: