Bug #15327: configure: --with-tcp-port option being partially ignored

make sure that if builder configured with a non-standard (!= 3306)
default TCP port that value actually gets used throughout. if they
didn't configure a value, assume "use a sensible default", which
will be read from /etc/services or, failing that, from the factory
default. That makes the order of preference
- command-line option
- my.cnf, where applicable
- $MYSQL_TCP_PORT environment variable
- /etc/services (unless configured --with-tcp-port)
- default port (--with-tcp-port=... or factory default)

scripts/mysql_config.sh

@@ -92,9 +92,14 @@ fix_path pkgincludedir include/mysql include
 
 version='@VERSION@'
 socket='@MYSQL_UNIX_ADDR@'
-port='@MYSQL_TCP_PORT@'
 ldflags='@LDFLAGS@'
 
+if [ @MYSQL_TCP_PORT_DEFAULT@ -eq 0 ]; then
+  port=0
+else
+  port=@MYSQL_TCP_PORT@
+fi
+
 # Create options 
 # We intentionally add a space to the beginning and end of lib strings, simplifies replace later
 libs=" $ldflags -L$pkglibdir -lmysqlclient @ZLIB_DEPS@ @NON_THREADED_LIBS@"