bug#64917: 30.0.50; c-ts-mode throws warnings about missing cpp support

[Robert Pluim]

I built master with tree-sitter support, and installed the c-language
grammar using M-x treesit-install-language-grammar. I have
libtree-sitter-c.so in ~/.emacs.d/tree-sitter

I restarted emacs, visited src/xdisp.c, and did M-x c-ts-mode, which
popped up a *Warnings* buffer containing:

⛔ Warning (treesit): Cannot activate tree-sitter, because language grammar for 
cpp is unavailable (not-found): (libtree-sitter-cpp libtree-sitter-cpp.0 
libtree-sitter-cpp.0.0 libtree-sitter-cpp.so libtree-sitter-cpp.so.0 
libtree-sitter-cpp.so.0.0) No such file or directory
⛔ Warning (treesit): Cannot activate tree-sitter, because language grammar for 
cpp is unavailable (not-found): (libtree-sitter-cpp libtree-sitter-cpp.0 
libtree-sitter-cpp.0.0 libtree-sitter-cpp.so libtree-sitter-cpp.so.0 
libtree-sitter-cpp.so.0.0) No such file or directory

which is less than desirable (althoug `major-mode' is c-ts-mode, so I
guess things worked)

Robert

In GNU Emacs 30.0.50 (build 24, x86_64-pc-linux-gnu, GTK+ Version
 3.24.37, cairo version 1.16.0) of 2023-07-28 built on rltb
Repository revision: a5dda9614a01ca753f25c904ccf7781176245b3c
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12009000
System Description: Debian GNU/Linux 12 (bookworm)

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3
ZLIB