component/haproxy: Provide QUIC enabled flavour of HAProxy

In the same time extract described variables to be available in the comment
context.

component/haproxy/buildout.cfg

@@ -22,22 +22,43 @@ configure-command = true
 # CPU is generic, and not native, as in SlapOS software released are
 # distributed in binary form, which may lead to incompatibility of such
 # compilation optimisation across various CPUs
+TARGET="$(uname -sr 2>/dev/null|grep -Eq '^Linux (2\.6\.2[89]|2\.6\.[3-9]|[3-9])' && echo linux-glibc || echo generic)"
+CPU=generic
+ARCH="$(uname -m 2>/dev/null|grep -E '^(x86_64|i[3456]86)$')"
+
+# By default haproxy is build w/o QUIC support
+SSL_INC=${openssl:location}/include
+SSL_LIB=${openssl:location}/lib
+SSL_ADDLIB=-Wl,-rpath=${openssl:location}/lib
+QUIC=
+
 make-options =
-  TARGET="$(uname -sr 2>/dev/null|grep -Eq '^Linux (2\.6\.2[89]|2\.6\.[3-9]|[3-9])' && echo linux-glibc || echo generic)"
-  CPU=generic
-  ARCH="$(uname -m 2>/dev/null|grep -E '^(x86_64|i[3456]86)$')"
+  TARGET=${:TARGET}
+  CPU=${:CPU}
+  ARCH=${:ARCH}
   PREFIX=@@LOCATION@@
   USE_DL=1
   USE_LUA=1
   LUA_INC=${lua:location}/include
   LUA_LIB=${lua:location}/lib
   USE_OPENSSL=1
-  SSL_INC=${openssl:location}/include
-  SSL_LIB=${openssl:location}/lib
+  SSL_INC=${:SSL_INC}
+  SSL_LIB=${:SSL_LIB}
+  ${:QUIC}
   USE_PCRE=1
   USE_ZLIB=1
   ZLIB_INC=${zlib:location}/include
   ZLIB_LIB=${zlib:location}/lib
-  ADDLIB="-Wl,-rpath=${openssl:location}/lib -Wl,-rpath=${pcre:location}/lib -Wl,-rpath=${zlib:location}/lib"
+  ADDLIB="${:SSL_ADDLIB} -Wl,-rpath=${pcre:location}/lib -Wl,-rpath=${zlib:location}/lib"
 environment =
   PATH=${pcre:location}/bin:%(PATH)s
+
+[haproxy-quic]
+<= haproxy
+
+SSL_INC=${openssl-quictls:location}/include
+SSL_LIB=${openssl-quictls:location}/lib
+SSL_ADDLIB=-Wl,-rpath=${openssl-quictls:location}/lib
+QUIC=USE_QUIC=1
+
+