bug#53050: 29.0.50; freetype font drivers reports invalid weight

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Do `M-x set-frame-font RET' on a build using a fontconfig-based font
driver (such as ftcrhb) and hit TAB.  There will be many fonts like
this:

  -1ASC-Liberation Mono-regular-italic-normal-*-*-*-*-*-m-0-iso10646-1
  -1ASC-Liberation Mono-regular-normal-normal-*-*-*-*-*-m-0-iso10646-1

Where the weight specification is `regular'.  The documentation for the
`weight' spec, however, says:

‘:weight’
     Font weight—one of the symbols (from densest to faintest)
     ‘ultra-bold’, ‘extra-bold’, ‘bold’, ‘semi-bold’, ‘normal’,
     ‘semi-light’, ‘light’, ‘extra-light’, or ‘ultra-light’.  On text
     terminals which support variable-brightness text, any weight
     greater than normal is displayed as extra bright, and any weight
     less than normal is displayed as half-bright.

Which doesn't include `regular' as a valid weight.  In Emacs 28, the
same fonts' weight attributes are also simply `normal'.

In GNU Emacs 29.0.50 (build 93, x86_64-pc-linux-gnu, GTK+ Version 3.24.30, cairo version 1.17.4)
 of 2022-01-06 built on trinity
Repository revision: 2ab73286b7a58eb983da21bca8b781ec884eb996
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101003
System Description: Fedora Linux 35 (Workstation Edition)

Configured using:
 'configure --cache-file=/tmp/ccache --with-xwidgets --with-xinput2'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG
RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS WEBP X11
XDBE XIM XINPUT2 XPM XWIDGETS GTK3 ZLIB

Important settings:
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media rmc puny
dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg
rfc6068 epg-config gnus-util text-property-search time-date seq gv
subr-x byte-opt bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget keymap hashtable-print-readable backquote threads
xwidget-internal dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
xinput2 x multi-tty make-network-process emacs)

Memory information:
((conses 16 44450 6418)
 (symbols 48 5670 1)
 (strings 32 17884 1243)
 (string-bytes 1 577300)
 (vectors 16 10772)
 (vector-slots 8 155225 10811)
 (floats 8 21 51)
 (intervals 56 202 0)
 (buffers 992 10))