databases/ldb20: fix build with lld 17

Building databases/ldb20 with lld 17 results in the following link
errors:

  ld: error: version script assignment of 'LDB_0.9.10' to symbol 'ldb_connect_backend' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.10' to symbol 'ldb_init_module_chain' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.10' to symbol 'ldb_load_modules_list' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_asq_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_paged_results_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_paged_searches_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_rdn_name_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_sample_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_server_sort_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_skel_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_0.9.18' to symbol 'ldb_tdb_init' failed: symbol not defined
  ld: error: version script assignment of 'LDB_1.1.25' to symbol 'ldb_unpack_data_only_attr_list' failed: symbol not defined
  ld: error: version script assignment of 'LDB_1.1.27' to symbol 'ldb_unpack_data_only_attr_list_flags' failed: symbol not defined
  ld: error: version script assignment of 'local' to symbol '_end' failed: symbol not defined
  ld: error: version script assignment of 'local' to symbol '__bss_start' failed: symbol not defined
  ld: error: version script assignment of 'local' to symbol '_edata' failed: symbol not defined

Since the linker version scripts are generated dynamically, suppress
errors with lld >= 17 due to these undefined symbols.

PR:		273753
MFH:		2023Q4

databases/ldb20/Makefile

@@ -90,7 +90,13 @@ PLIST_FILES=		include/ldb_version.h \
 
 .include <bsd.port.pre.mk>
 
-CONFIGURE_ENV+=		CFLAGS=-I${LOCALBASE}/include LDFLAGS=-L${LOCALBASE}/lib
+CFLAGS+=		-I${LOCALBASE}/include
+LDFLAGS+=		-L${LOCALBASE}/lib
+
+# Some symbols in ldb's linker version scripts are not defined, but since the
+# scripts are generated dynamically, suppress errors with lld >= 17 due to these
+# undefined symbols.
+LDFLAGS+=		-Wl,--undefined-version
 
 .if ! ${PORT_OPTIONS:MMANPAGES}
 CONFIGURE_ENV+=		XSLTPROC="true"