SDL_GetPowerInfo_Hardwired is static in SDL_power.c .. therefore, comment out its extern declaration in SDL_syspower.h.
diff --git a/src/power/SDL_syspower.h b/src/power/SDL_syspower.h
index a9bf70c..afd6268 100644
--- a/src/power/SDL_syspower.h
+++ b/src/power/SDL_syspower.h
@@ -40,7 +40,9 @@ SDL_bool SDL_GetPowerInfo_Android(SDL_PowerState *, int *, int *);
SDL_bool SDL_GetPowerInfo_PSP(SDL_PowerState *, int *, int *);
SDL_bool SDL_GetPowerInfo_WinRT(SDL_PowerState *, int *, int *);
SDL_bool SDL_GetPowerInfo_Emscripten(SDL_PowerState *, int *, int *);
-SDL_bool SDL_GetPowerInfo_Hardwired(SDL_PowerState *, int *, int *);
+
+/* this one is static in SDL_power.c */
+/* SDL_bool SDL_GetPowerInfo_Hardwired(SDL_PowerState *, int *, int *);*/
#endif /* SDL_syspower_h_ */