fix: ship libquiche.so.0 into runtime image so curl -V works

libcurl.so.4 is dynamically linked against libquiche.so.0 (DT_SONAME), but
the runtime stage only copies /curl/usr/local/ and the embedded rpath pointed
at the builder-only path /opt/quiche-src/target/release. The result: the final
image was missing libquiche.so.0, so 'curl -V' died with

  Error loading shared library libquiche.so.0: No such file or directory
  Error relocating .../libcurl.so.4: quiche_* symbol not found

This went undetected because 'Test curl -V' is gated 'if: github.event_name
!= push', so push builds never ran it; the weekly schedule run is what first
exercised the broken image.

Install libquiche.so.0 (+ .so symlink) into /curl/usr/local/lib and repoint
the rpath at /usr/local/lib so the loader finds it in the final image.
Verified locally (native arm64): curl -V exits 0, reports quiche/0.29.0,
ldd resolves libquiche.so.0 => /usr/local/lib/libquiche.so.0.

Author: dvershinin

Dockerfile

@@ -32,9 +32,14 @@ RUN mkdir -p /opt/curl-src && \
     rm /opt/curl.tar.gz
 RUN cd /opt/curl-src && \
     autoreconf -fi && \
-    ./configure LDFLAGS="-Wl,-rpath,/opt/quiche-src/target/release" --with-openssl=/opt/quiche-src/quiche/deps/boringssl/src --with-quiche=/opt/quiche-src/target/release --with-nghttp2 --with-zlib && \
+    ./configure LDFLAGS="-Wl,-rpath,/usr/local/lib" --with-openssl=/opt/quiche-src/quiche/deps/boringssl/src --with-quiche=/opt/quiche-src/target/release --with-nghttp2 --with-zlib && \
     make -j $(nproc) && \
-    make DESTDIR="/curl/" install
+    make DESTDIR="/curl/" install && \
+    # libcurl.so.4 dynamically NEEDs libquiche.so.0; ship it into the runtime
+    # image (only /curl/usr/local is copied to the final stage) and point the
+    # rpath above at /usr/local/lib so the loader finds it there.
+    install -D -m755 /opt/quiche-src/target/release/libquiche.so /curl/usr/local/lib/libquiche.so.0 && \
+    ln -sf libquiche.so.0 /curl/usr/local/lib/libquiche.so
 
 FROM alpine:edge
 RUN apk add --no-cache nghttp2 zlib libpsl bash perl ca-certificates