Revert "build: cmake: use -O0 for debug build"

This reverts commit 8a54e478ba. As
commit 7dadd38161 ("Revert "configure: Switch debug build from
-O0 to -Og") was reverted (by b7627085cb, "Revert "Revert
"configure: Switch debug build from -O0 to -Og""")), we do the
same to cmake to keep the two build systems in sync.

Closes #14286

cmake/mode.DEBUG.cmake

@@ -1,4 +1,9 @@
-set(default_Seastar_OptimizationLevel_DEBUG "0")
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64")
+  # -fasan -Og breaks some coroutines on aarch64, use -O0 instead
+  set(default_Seastar_OptimizationLevel_DEBUG "0")
+else()
+  set(default_Seastar_OptimizationLevel_DEBUG "g")
+endif()
 set(Seastar_OptimizationLevel_DEBUG
   ${default_Seastar_OptimizationLevel_DEBUG}
   CACHE