logging: v2: workaround for old toolchains when !LOG

For GCC < 4.9.0 and Clang < 3.8.0, auto type is not supported.
But the previous behavior to depend on CONFIG_LOG2_ALWAYS_RUNTIME
to be enabled doesn't work because this kconfig is not available
when CONFIG_LOG is not enabled, as LOG_*() are still being
expanded when CONFIG_LOG=n, resulting in toolchain complaining
about unknown keyword. So when CONFIG_LOG=n and old toolchains,
force it to use runtime packaging to avoid the issue.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>