[Build] Add AM_OBJCXXFLAGS and QT_PIE_FLAGS to OBJCXXFLAGS to future-proof darwin targets

Author: fanquake

src/Makefile.qt.include

@@ -368,6 +368,7 @@ BITCOIN_QT_INCLUDES = -I$(builddir)/qt -I$(srcdir)/qt -I$(srcdir)/qt/forms \
 qt_libbitcoinqt_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(BITCOIN_QT_INCLUDES) \
   $(QT_INCLUDES) $(QT_DBUS_INCLUDES) $(PROTOBUF_CFLAGS) $(QR_CFLAGS)
 qt_libbitcoinqt_a_CXXFLAGS = $(AM_CXXFLAGS) $(QT_PIE_FLAGS)
+qt_libbitcoinqt_a_OBJCXXFLAGS = $(AM_OBJCXXFLAGS) $(QT_PIE_FLAGS)
 
 qt_libbitcoinqt_a_SOURCES = $(BITCOIN_QT_CPP) $(BITCOIN_QT_H) $(QT_FORMS_UI) \
   $(QT_QRC) $(QT_QRC_LOCALE) $(QT_TS) $(PROTOBUF_PROTO) $(RES_ICONS) $(RES_IMAGES) $(RES_MOVIES)