According to page 118 of SHC Manual (Hitachi C Compiler for SuperH),
the compiler implicitly defines macros __HITACHI__ and
__HITACHI_VERSION__ in the format aabb, where aa is version and bb is
revision.
Examples provided were:
#define __HITACHI_VERSION__ 0x0501 /* Version 5.1C */
#define __HITACHI_VERSION__ 0x0600 /* Version 6.0 */
Also, the page references several compiler toggles that can be "relayed" to the source code via macros, such as cpu type, endianness, double=float, etc.
From this information, one can write code that can be compiled either with
GCC or SHC (Casio Official SDK).
Example:
if defined(__HITACHI__) && !defined(__GNUC__)
/* code for official sdk here */
#elif defined(__GNUC__)
/* code for gcc here */
#endif