Support both build-time and run-time values for WEBAPP_URL. Improve re-build time, if just the WEBAPP_URL is changed.

Dockerfile

@@ -8,9 +8,7 @@ ARG NEXTAUTH_SECRET=secret
 ARG CALENDSO_ENCRYPTION_KEY=secret
 ARG MAX_OLD_SPACE_SIZE=4096
 
-# PLACEHOLDER value is compiled in during build, but will be replaced it at runtime
-#             see: scripts/replace-placeholders.sh
-ENV NEXT_PUBLIC_WEBAPP_URL=https://NEXT_PUBLIC_WEBAPP_URL_PLACEHOLDER \
+ENV NEXT_PUBLIC_WEBAPP_URL=http://NEXT_PUBLIC_WEBAPP_URL_PLACEHOLDER \
     NEXT_PUBLIC_LICENSE_CONSENT=$NEXT_PUBLIC_LICENSE_CONSENT \
     CALCOM_TELEMETRY_DISABLED=$CALCOM_TELEMETRY_DISABLED \
     DATABASE_URL=$DATABASE_URL \
@@ -30,6 +28,8 @@ RUN yarn build
 FROM node:16 as runner
 
 WORKDIR /calcom
+ARG NEXT_PUBLIC_WEBAPP_URL=http://localhost:3000
+
 ENV NODE_ENV production
 
 RUN apt-get update && \
@@ -44,5 +44,12 @@ COPY --from=builder /calcom/apps/web ./apps/web
 COPY --from=builder /calcom/packages/prisma/schema.prisma ./prisma/schema.prisma
 COPY scripts scripts
 
+# Save value used during this build stage. If NEXT_PUBLIC_WEBAPP_URL and BUILT_NEXT_PUBLIC_WEBAPP_URL differ at
+# run-time, then start.sh will find/replace static values again.
+ENV NEXT_PUBLIC_WEBAPP_URL=$NEXT_PUBLIC_WEBAPP_URL \
+    BUILT_NEXT_PUBLIC_WEBAPP_URL=$NEXT_PUBLIC_WEBAPP_URL
+
+RUN scripts/replace-placeholder.sh http://NEXT_PUBLIC_WEBAPP_URL_PLACEHOLDER ${NEXT_PUBLIC_WEBAPP_URL}
+
 EXPOSE 3000
 CMD ["/calcom/scripts/start.sh"]