crimson/osd: disable var-tracking-assignments

crimson/osd: disable var-tracking-assignments

to disable following warning:

In file included from ../src/common/config.h:27,
                 from ../src/crimson/common/config_proxy.h:8,
                 from ../src/crimson/osd/main.cc:23:
../src/common/config_values.h: In copy constructor ‘ConfigValues::ConfigValues(const ConfigValues&)’:
../src/common/config_values.h:19:7: note: variable tracking size limit exceeded with ‘-fvar-tracking-assignments’, retrying without
   19 | class ConfigValues {
      |       ^~~~~~~~~~~~

Signed-off-by: Kefu Chai <kchai@redhat.com>