message: Fix compile issue on some platforms.
  Compilation was failing when on native windows.
diff: @@ -458,7 +458,7 @@ endif
  libbitcoinconsensus_la_LDFLAGS = $(AM_LDFLAGS) $(BOOST_LIBS) -no-undefined $(RELDFLAGS)
  libbitcoinconsensus_la_LIBADD = $(LIBSECP256K1)
  -libbitcoinconsensus_la_CPPFLAGS = $(AM_CPPFLAGS) -I$(builddir)/obj -I$(srcdir)/secp256k1/include -DBUILD_BITCOIN_INTERNAL
  +libbitcoinconsensus_la_CPPFLAGS = $(AM_CPPFLAGS) -I$(BOOST_CPPFLAGS) -I$(builddir)/obj -I$(srcdir)/secp256k1/include -DBUILD_BITCOIN_INTERNAL
  libbitcoinconsensus_la_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
  endif
  