ncurses: fix build on NetBSD

Only tested cross-compiling, but is probably necessary for native too.

Fixes errors like this:

linking ../lib/libncursesw.so
x86_64-unknown-netbsd-gcc  --param max-inline-insns-single=1200 -Wl,-shared -Wl,-Bshareable -o ../lib/libncursesw.so ../obj_s/hardscroll.o ../obj_s/hashmap.o ../obj_s/lib_addch.o ../obj_s/lib_addstr.o ../obj_s/lib_beep.o ../obj_s/lib_bkgd.o ../obj_s/lib_box.o ../obj_s/lib_chgat.o ../obj_s/lib_clear.o ../obj_s/lib_clearok.o ../obj_s/lib_clrbot.o ../obj_s/lib_clreol.o ../obj_s/lib_color.o ../obj_s/lib_colorset.o ../obj_s/lib_delch.o ../obj_s/lib_delwin.o ../obj_s/lib_echo.o ../obj_s/lib_endwin.o ../obj_s/lib_erase.o ../obj_s/lib_flash.o ../obj_s/lib_gen.o ../obj_s/lib_getch.o ../obj_s/lib_getstr.o ../obj_s/lib_hline.o ../obj_s/lib_immedok.o ../obj_s/lib_inchstr.o ../obj_s/lib_initscr.o ../obj_s/lib_insch.o ../obj_s/lib_insdel.o ../obj_s/lib_insnstr.o ../obj_s/lib_instr.o ../obj_s/lib_isendwin.o ../obj_s/lib_leaveok.o ../obj_s/lib_mouse.o ../obj_s/lib_move.o ../obj_s/lib_mvcur.o ../obj_s/lib_mvwin.o ../obj_s/lib_newterm.o ../obj_s/lib_newwin.o ../obj_s/lib_nl.o ../obj_s/lib_overlay.o ../obj_s/lib_pad.o ../obj_s/lib_printw.o ../obj_s/lib_redrawln.o ../obj_s/lib_refresh.o ../obj_s/lib_restart.o ../obj_s/lib_scanw.o ../obj_s/lib_screen.o ../obj_s/lib_scroll.o ../obj_s/lib_scrollok.o ../obj_s/lib_scrreg.o ../obj_s/lib_set_term.o ../obj_s/lib_slk.o ../obj_s/lib_slkatr_set.o ../obj_s/lib_slkatrof.o ../obj_s/lib_slkatron.o ../obj_s/lib_slkatrset.o ../obj_s/lib_slkattr.o ../obj_s/lib_slkclear.o ../obj_s/lib_slkcolor.o ../obj_s/lib_slkinit.o ../obj_s/lib_slklab.o ../obj_s/lib_slkrefr.o ../obj_s/lib_slkset.o ../obj_s/lib_slktouch.o ../obj_s/lib_touch.o ../obj_s/lib_tstp.o ../obj_s/lib_ungetch.o ../obj_s/lib_vidattr.o ../obj_s/lib_vline.o ../obj_s/lib_wattroff.o ../obj_s/lib_wattron.o ../obj_s/lib_winch.o ../obj_s/lib_window.o ../obj_s/nc_panel.o ../obj_s/safe_sprintf.o ../obj_s/tty_update.o ../obj_s/varargs.o ../obj_s/vsscanf.o ../obj_s/lib_freeall.o ../obj_s/charable.o ../obj_s/lib_add_wch.o ../obj_s/lib_box_set.o ../obj_s/lib_cchar.o ../obj_s/lib_erasewchar.o ../obj_s/lib_get_wch.o ../obj_s/lib_get_wstr.o ../obj_s/lib_hline_set.o ../obj_s/lib_in_wch.o ../obj_s/lib_in_wchnstr.o ../obj_s/lib_ins_wch.o ../obj_s/lib_inwstr.o ../obj_s/lib_key_name.o ../obj_s/lib_pecho_wchar.o ../obj_s/lib_slk_wset.o ../obj_s/lib_unget_wch.o ../obj_s/lib_vid_attr.o ../obj_s/lib_vline_set.o ../obj_s/lib_wacs.o ../obj_s/lib_wunctrl.o ../obj_s/expanded.o ../obj_s/legacy_coding.o ../obj_s/lib_dft_fgbg.o ../obj_s/lib_print.o ../obj_s/new_pair.o ../obj_s/resizeterm.o ../obj_s/use_screen.o ../obj_s/use_window.o ../obj_s/wresize.o ../obj_s/access.o ../obj_s/add_tries.o ../obj_s/alloc_ttype.o ../obj_s/codes.o ../obj_s/comp_captab.o ../obj_s/comp_error.o ../obj_s/comp_hash.o ../obj_s/comp_userdefs.o ../obj_s/db_iterator.o ../obj_s/doalloc.o ../obj_s/entries.o ../obj_s/fallback.o ../obj_s/free_ttype.o ../obj_s/getenv_num.o ../obj_s/home_terminfo.o ../obj_s/init_keytry.o ../obj_s/lib_acs.o ../obj_s/lib_baudrate.o ../obj_s/lib_cur_term.o ../obj_s/lib_data.o ../obj_s/lib_has_cap.o ../obj_s/lib_kernel.o ../obj_s/lib_keyname.o ../obj_s/lib_longname.o ../obj_s/lib_napms.o ../obj_s/lib_options.o ../obj_s/lib_raw.o ../obj_s/lib_setup.o ../obj_s/lib_termcap.o ../obj_s/lib_termname.o ../obj_s/lib_tgoto.o ../obj_s/lib_ti.o ../obj_s/lib_tparm.o ../obj_s/lib_tputs.o ../obj_s/lib_trace.o ../obj_s/lib_ttyflags.o ../obj_s/lib_twait.o ../obj_s/name_match.o ../obj_s/names.o ../obj_s/obsolete.o ../obj_s/read_entry.o ../obj_s/read_termcap.o ../obj_s/strings.o ../obj_s/tries.o ../obj_s/trim_sgr0.o ../obj_s/unctrl.o ../obj_s/visbuf.o ../obj_s/alloc_entry.o ../obj_s/captoinfo.o ../obj_s/comp_expand.o ../obj_s/comp_parse.o ../obj_s/comp_scan.o ../obj_s/parse_entry.o ../obj_s/write_entry.o ../obj_s/define_key.o ../obj_s/hashed_db.o ../obj_s/key_defined.o ../obj_s/keybound.o ../obj_s/keyok.o ../obj_s/version.o -L../lib
/nix/store/6h96vn8vpm01sn0r5shdl48nw94kzls6-x86_64-unknown-netbsd-binutils-2.35.1/bin/x86_64-unknown-netbsd-ld: /nix/store/dy4bg91z7g0p8k3cdq8rbmzj27lsmx5k-libc-netbsd-9.1-x86_64-unknown-netbsd/lib/crt0.o: in function `__start':
(.text+0x31): undefined reference to `__fini_array_start'
/nix/store/6h96vn8vpm01sn0r5shdl48nw94kzls6-x86_64-unknown-netbsd-binutils-2.35.1/bin/x86_64-unknown-netbsd-ld: /nix/store/dy4bg91z7g0p8k3cdq8rbmzj27lsmx5k-libc-netbsd-9.1-x86_64-unknown-netbsd/lib/crt0.o: relocation R_X86_64_PC32 against undefined hidden symbol `__fini_array_start' can not be used when making a shared object
/nix/store/6h96vn8vpm01sn0r5shdl48nw94kzls6-x86_64-unknown-netbsd-binutils-2.35.1/bin/x86_64-unknown-netbsd-ld: final link failed: bad value
collect2: error: ld returned 1 exit status

pkgs/development/libraries/ncurses/default.nix

@@ -42,6 +42,7 @@ stdenv.mkDerivation rec {
   ] ++ lib.optional unicode "--enable-widec"
     ++ lib.optional (!withCxx) "--without-cxx"
     ++ lib.optional (abiVersion == "5") "--with-abi-version=5"
+    ++ lib.optional stdenv.hostPlatform.isNetBSD "--enable-rpath"
     ++ lib.optionals stdenv.hostPlatform.isWindows [
       "--enable-sp-funcs"
       "--enable-term-driver"