Problem: address sanitizer support in CI is hacky

Solution: import better solution from zproject and add a new autoconf
option

ci_build.sh

@@ -16,8 +16,7 @@ if [ $BUILD_TYPE == "default" ]; then
     CONFIG_OPTS+=("--prefix=${BUILD_PREFIX}")
 
     if [ -n "$ADDRESS_SANITIZER" ] && [ "$ADDRESS_SANITIZER" == "enabled" ]; then
-        CONFIG_OPTS+=("CFLAGS=-fsanitize=address")
-        CONFIG_OPTS+=("CXXFLAGS=-fsanitize=address")
+        CONFIG_OPTS+=("--enable-address-sanitizer=yes")
     fi
 
     if [ -z $CURVE ]; then

configure.ac

@@ -127,6 +127,22 @@ if test "x$zmq_militant" = "xyes"; then
     AC_DEFINE(ZMQ_ACT_MILITANT, 1, [Enable militant API assertions])
 fi
 
+# Memory mis-use detection
+AC_MSG_CHECKING([whether to enable ASan])
+AC_ARG_ENABLE(address-sanitizer, [AS_HELP_STRING([--enable-address-sanitizer=yes/no],
+                  [Build with GCC Address Sanitizer instrumentation])],
+                  [ZMQ_ASAN="$enableval"])
+
+if test "x${ZMQ_ASAN}" == "xyes"; then
+    CFLAGS="${CFLAGS} -fsanitize=address"
+    CXXFLAGS="${CXXFLAGS} -fsanitize=address"
+
+    AM_CONDITIONAL(ENABLE_ASAN, true)
+    AC_MSG_RESULT([yes])
+else
+    AM_CONDITIONAL(ENABLE_ASAN, false)
+    AC_MSG_RESULT([no])
+fi
 
 # By default compiling with -Werror except OSX.
 libzmq_werror="yes"