meson-buildoptions: Remove duplicated entry of --gdb in the help text

Since --gdb has recently been added to meson_options.txt, the help
text shows up twice in the output of "./configure --help":

 $ ./configure --help | grep gdb
   --gdb=GDB-path           gdb to use for gdbstub tests [/usr/bin/gdb]
   --gdb=VALUE              Path to GDB

As the probed value is of interest we want to keep the configure text
so make meson-buildoptions able to handle deferring to configure.

Fixes: b46b3818cf ("tests/functional: Provide GDB to the functional tests")
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Tested-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20260203115201.2387721-2-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

scripts/meson-buildoptions.py

@@ -53,6 +53,11 @@ AUTO_OPTIONS = {
     "werror",
 }
 
+# Options that configure prints help for, so we can skip
+CONFIGURE_HELP = {
+    "gdb",
+}
+
 # Builtin options that should be definable via configure.  Some of the others
 # we really do not want (e.g. c_args is defined via the native file, not
 # via -D, because it's a mix of CFLAGS and --extra-cflags); for specific
@@ -189,7 +194,9 @@ def print_help(options):
         key = cli_help_key(opt)
         # The first section includes options that have an arguments,
         # and booleans (i.e., only one of enable/disable makes sense)
-        if require_arg(opt):
+        if opt["name"] in CONFIGURE_HELP:
+            pass
+        elif require_arg(opt):
             metavar = cli_metavar(opt)
             left = f"--{key}={metavar}"
             help_line(left, opt, 27, True)

scripts/meson-buildoptions.sh

@@ -58,7 +58,6 @@ meson_options_help() {
   printf "%s\n" '  --enable-ubsan           enable undefined behaviour sanitizer'
   printf "%s\n" '  --firmwarepath=VALUES    search PATH for firmware files [share/qemu-'
   printf "%s\n" '                           firmware]'
-  printf "%s\n" '  --gdb=VALUE              Path to GDB'
   printf "%s\n" '  --iasl=VALUE             Path to ACPI disassembler'
   printf "%s\n" '  --includedir=VALUE       Header file directory [include]'
   printf "%s\n" '  --interp-prefix=VALUE    where to find shared libraries etc., use %M for'