refactor: extract shared nginx build config to conf/nginx-configure-flags

Moves version variables and configure flags to a single sourced file,
eliminating duplication between bin/compile and the release workflow.

bin/compile

@@ -3,16 +3,10 @@
 set -eo pipefail
 [[ $TRACE ]] && set -x
 
-# https://nginx.org/en/download.html
-NGINX_VERSION="1.29.8"
+# shellcheck source=conf/nginx-configure-flags
+source "$(cd "$(dirname "$0")" && cd .. && pwd)/conf/nginx-configure-flags"
 NGINX_TARBALL="nginx-${NGINX_VERSION}.tar.gz"
-# https://github.com/PCRE2Project/pcre2/releases
-PCRE_VERSION="10.47"
 PCRE_TARBALL="pcre2-${PCRE_VERSION}.tar.gz"
-# https://github.com/gliderlabs/sigil/releases
-SIGIL_VERSION="0.11.5"
-# https://github.com/madler/zlib/releases
-ZLIB_VERSION="1.3.2"
 ZLIB_TARBALL="zlib-${ZLIB_VERSION}.tar.gz"
 BUILDPACK_REPO="dokku/heroku-buildpack-nginx"
 
@@ -103,40 +97,10 @@ else
   echo "-----> Compiling static nginx binary"
   mkdir "$BUILD_DIR/nginx"
   suppress ./configure \
-    --with-cpu-opt=generic \
     --prefix="$BUILD_DIR/nginx" \
     --with-pcre=../pcre2-${PCRE_VERSION} \
-    --sbin-path=. \
-    --pid-path=./nginx.pid \
-    --conf-path=./nginx.conf \
-    --with-ld-opt="-static" \
-    --with-http_stub_status_module \
-    --with-http_gzip_static_module \
-    --with-file-aio \
     --with-zlib=../zlib-${ZLIB_VERSION} \
-    --with-pcre \
-    --with-cc-opt="-O2 -static -static-libgcc" \
-    --without-http_ssi_module \
-    --without-http_userid_module \
-    --without-http_access_module \
-    --without-http_autoindex_module \
-    --without-http_geo_module \
-    --without-http_map_module \
-    --without-http_split_clients_module \
-    --without-http_referer_module \
-    --without-http_fastcgi_module \
-    --without-http_uwsgi_module \
-    --without-http_scgi_module \
-    --without-http_memcached_module \
-    --without-http_empty_gif_module \
-    --without-http_browser_module \
-    --without-http_upstream_ip_hash_module \
-    --without-http_upstream_least_conn_module \
-    --without-http_upstream_keepalive_module \
-    --without-mail_pop3_module \
-    --without-mail_imap_module \
-    --without-mail_smtp_module \
-    --with-http_realip_module
+    "${NGINX_CONFIGURE_FLAGS[@]}"
 
   sed -i "/CFLAGS/s/ \-O //g" objs/Makefile