[Build] Do not enforce use of InlineIsEqualGUID in release builds.

Non-inlined version resolves to memcmp() and sane compilers
inline memcmp() for small memory chunks (when some optimization is on).
[Build] Break one bug add_dinitions into multiple ones.

 * Move -D_CRT_NON_CONFORMING_SWPRINTFS to gcc-specific branch.
 * Add some comments explaining why the particular definition is used.