scripts/gdb: raise error with reduced debugging information

If CONFIG_DEBUG_INFO_REDUCED is enabled in the kernel configuration, we
will typically not be able to load vmlinux-gdb.py and will fail with:

Traceback (most recent call last):
  File "/home/fainelli/work/buildroot/output/arm64/build/linux-custom/vmlinux-gdb.py", line 25, in <module>
    import linux.utils
  File "/home/fainelli/work/buildroot/output/arm64/build/linux-custom/scripts/gdb/linux/utils.py", line 131, in <module>
    atomic_long_counter_offset = atomic_long_type.get_type()['counter'].bitpos
KeyError: 'counter'

Rather be left wondering what is happening only to find out that reduced
debug information is the cause, raise an eror.  This was not typically a
problem until e3c8d33e0d ("scripts/gdb: fix 'lx-dmesg' on 32 bits arch")
but it has since then.

Link: https://lkml.kernel.org/r/20230406215252.1580538-1-f.fainelli@gmail.com
Fixes: e3c8d33e0d ("scripts/gdb: fix 'lx-dmesg' on 32 bits arch")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: Antonio Borneo <antonio.borneo@foss.st.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/gdb/linux/constants.py.in

@@ -40,6 +40,8 @@
 
 import gdb
 
+LX_CONFIG(CONFIG_DEBUG_INFO_REDUCED)
+
 /* linux/clk-provider.h */
 if IS_BUILTIN(CONFIG_COMMON_CLK):
     LX_GDBPARSED(CLK_GET_RATE_NOCACHE)

scripts/gdb/vmlinux-gdb.py

@@ -22,6 +22,10 @@ except:
     gdb.write("NOTE: gdb 7.2 or later required for Linux helper scripts to "
               "work.\n")
 else:
+    import linux.constants
+    if linux.constants.LX_CONFIG_DEBUG_INFO_REDUCED:
+        raise gdb.GdbError("Reduced debug information will prevent GDB "
+                           "from having complete types.\n")
     import linux.utils
     import linux.symbols
     import linux.modules
@@ -32,7 +36,6 @@ else:
     import linux.lists
     import linux.rbtree
     import linux.proc
-    import linux.constants
     import linux.timerlist
     import linux.clk
     import linux.genpd