support/scripts/gen-bootin-toolchains: arcle-750d toolchain has no gdbserver

Since the build of gdbserver for ARC 750D is broken, Bootlin
toolchains since 2024.05 no longer provide gdbserver for ARC, causing
build failures when the autobuilders try to use it. Let's fix this by
telling gen-bootlin-toolchains that the arcle-750d toolchains don't
have gdbserver.

Fixes:

  https://autobuild.buildroot.net/results/77c865f941612e99d8b6a7f66b5bc06f90d6b7db/

Cc: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
Cc: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>
(cherry picked from commit edac3dba3b)
[Titouan: Fix merge conflicts for 2025.02.x]
Signed-off-by: Titouan Christophe <titouan.christophe@mind.be>

support/scripts/gen-bootlin-toolchains

@@ -36,6 +36,7 @@ arches = {
     'arcle-750d': {
         'conditions': ['BR2_arcle', 'BR2_arc750d'],
         'prefix': 'arc',
+        'gdbserver': False,
     },
     'arcle-hs38': {
         'conditions': ['BR2_arcle', 'BR2_archs38'],