Refactor platform logic within print.h (#11863)

* Remove GCC check from debug

* Remove platform logic from common.mk

* Refactor platform logic within print.h

* restore debug.c format

* headers

* Rename function pointer type

* review comments

* Update tmk_core/common/printf.c

Co-authored-by: Nick Brassel <nick@tzarc.org>

* Format

Co-authored-by: Nick Brassel <nick@tzarc.org>

tmk_core/common/sendchar.h

@@ -23,6 +23,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 extern "C" {
 #endif
 
+typedef int8_t (*sendchar_func_t)(uint8_t c);
+
 /* transmit a character.  return 0 on success, -1 on error. */
 int8_t sendchar(uint8_t c);