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.

conf/nginx-configure-flags

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+# Shared nginx build configuration
+# Sourced by bin/compile and .github/workflows/release.yml
+# shellcheck disable=SC2034
+
+# https://nginx.org/en/download.html
+NGINX_VERSION="1.29.8"
+# https://github.com/PCRE2Project/pcre2/releases
+PCRE_VERSION="10.47"
+# https://github.com/gliderlabs/sigil/releases
+SIGIL_VERSION="0.11.5"
+# https://github.com/madler/zlib/releases
+ZLIB_VERSION="1.3.2"
+
+NGINX_CONFIGURE_FLAGS=(
+  --with-cpu-opt=generic
+  --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-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
+)