small adjustment, gtk2 not needed as explicit CPPFLAGS argument

d4x/d4x.spec

@@ -79,7 +79,7 @@ AutoReqProv:  no
     CXX="%{l_cxx}" \
     CFLAGS="%{l_cflags -O}" \
     CXXFLAGS="%{l_cxxflags -O}" \
-    CPPFLAGS="%{l_cppflags gtk2}" \
+    CPPFLAGS="%{l_cppflags}" \
     LDFLAGS="%{l_ldflags}" \
     ./configure \
         --prefix=%{l_prefix} \