put an end to builds failing due to gpg key import

Dockerfile

@@ -1,6 +1,5 @@
 ARG NGINX_VERSION=1.18.0
 ARG NGX_BROTLI_COMMIT=25f86f0bac1101b6512135eac5f93c49c63609e3
-ARG GPG_KEYS=B0F4253373F8F6F510D42178520A9993A1C052F8
 ARG CONFIG="\
 		--prefix=/etc/nginx \
 		--sbin-path=/usr/sbin/nginx \
@@ -53,7 +52,6 @@ LABEL maintainer="NGINX Docker Maintainers <docker-maint@nginx.com>"
 
 ARG NGINX_VERSION
 ARG NGX_BROTLI_COMMIT
-ARG GPG_KEYS
 ARG CONFIG
 
 RUN \
@@ -78,6 +76,8 @@ RUN \
 		g++ \
 		cmake
 
+COPY nginx.pub /tmp/nginx.pub
+
 RUN \
 	mkdir -p /usr/src/ngx_brotli \
 	&& cd /usr/src/ngx_brotli \
@@ -91,7 +91,7 @@ RUN \
 	&& curl -fSL https://nginx.org/download/nginx-$NGINX_VERSION.tar.gz.asc  -o nginx.tar.gz.asc \
         && sha512sum nginx.tar.gz nginx.tar.gz.asc \
 	&& export GNUPGHOME="$(mktemp -d)" \
-	&& gpg --keyserver ipv4.pool.sks-keyservers.net --recv-keys "$GPG_KEYS" \
+	&& gpg --import /tmp/nginx.pub \
 	&& gpg --batch --verify nginx.tar.gz.asc nginx.tar.gz \
 	&& mkdir -p /usr/src \
 	&& tar -zxC /usr/src -f nginx.tar.gz

nginx.pub

@@ -0,0 +1,29 @@
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+=NeQn
+-----END PGP PUBLIC KEY BLOCK-----