Fix the missing lz on id3tag problem on cygwin

configure.in

@@ -19,7 +19,6 @@ rend_posix=true
 STATIC_LIBS=no
 CPPFLAGS="${CPPFLAGS} -g"
 
-AC_CHECK_LIB(z,compress,LDFLAGS="$LDFLAGS -lz",echo "Must have zlib";exit)
 AC_CHECK_LIB(pthread,pthread_create,LDFLAGS="$LDFLAGS -lpthread")
 
 AC_ARG_ENABLE(debug,[  --enable-debug          Enable debugging features],
@@ -150,15 +149,20 @@ fi
 
 AC_CHECK_HEADERS(id3tag.h,, [
  AC_MSG_ERROR([id3tag.h not found... try --with-id3tag=dir])])
+
+oldcflags=$CFLAGS
+
+CFLAGS="$CFLAGS -lz"
 AC_CHECK_LIB(id3tag,id3_file_open,echo "Have id3tag",echo "Must have libid3tag";exit)
 
 if test "$STATIC_LIBS" != "no"; then
-  LDFLAGS="${LDFLAGS} ${STATIC_LIBS}/libid3tag.a"
+  LDFLAGS="${LDFLAGS} ${STATIC_LIBS}/libid3tag.a -lz"
   echo "Adding static libid3tag"
 else
-  LDFLAGS="${LDFLAGS} -lid3tag"
+  LDFLAGS="${LDFLAGS} -lid3tag -lz"
   echo "Adding dynamic libid3tag"
 fi
+CFLAGS=$oldcflags
 
 echo USE_OGGVORBIS is $use_oggvorbis