Install libpcre2-dev alongside regex-pcre2

Otherwise linking against libpcre2 will fail, as libghc-regex-pcre2-dev
does not depend on libpcre2-dev.

Author: apoikos

ganeti/Dockerfile.debian-testing

@@ -28,7 +28,7 @@ RUN apt-get update && apt-get install --yes --no-install-recommends \
   libghc-hinotify-dev \
   libghc-base64-bytestring-dev \
   libghc-zlib-dev \
-  libghc-regex-pcre2-dev \
+  libghc-regex-pcre2-dev libpcre2-dev \
   libghc-regex-tdfa-dev \
   libghc-attoparsec-dev \
   libghc-vector-dev \