RTC fails when running an ELF

[PikalaxALT]

To test:

1. Clone pokeemerald from this branch
2. Follow the instructions in INSTALL.md to build Pokemon Emerald (USA)
3. Launch pokeemerald.gba and play to the main menu (NEW GAME/OPTIONS).
4. Do the same with pokeemerald.elf and notice that the internal battery has run dry.

Note: I looked at the game pak overrides menu and observed that RTC and Flash 1M were correctly detected for both the GBA and ELF formats.

[PikalaxALT]

I should also mention the following (and I'll comment similarly on #1450): This ELF has a correct ROM header courtesy of a change I made to the gbafix utility. The game plays normally aside from the RTC issue. Notably, no such issue arises on the full version of no$gba debugger.

System info

Windows 10-1809 Intel CORE i5 x86_64
mGBA v0.7.2 from the 64-bit Windows installer