fix gcc15 issues

[bitten2up]

adds two flags (-std=c11 and -Wno-incompatible-pointer-types)' to prevent compiler errors on gcc 15

In file included from arena_alloc.c:24:
types.h:8:21: error: ‘bool’ cannot be defined via ‘typedef’
    8 | typedef signed char bool;
      |                     ^~~~

(this one is sdl exclusive)

src/lib/m4a/m4a.c: In function ‘MPlayExtender’:
src/lib/m4a/m4a.c:266:24: error: assignment to ‘MPlayFunc’ {aka ‘void (*)(void)’} from incompatible pointer type ‘void (*)(struct MP2KPlayerState *, struct MP2KTrack *)’ [-Wincompatible-pointer-types]
  266 |     gMPlayJumpTable[8] = MP2K_event_memacc;

[JaceCear]

This warning should not be removed, I think.

[JaceCear]

include/lib/m4a/m4a_internal.h:extern MPlayFunc gMPlayJumpTable[];
is
include/lib/m4a/m4a_internal.h:extern void *gMPlayJumpTable[];
in SA2, feel free to adjust that.
As well as
src/lib/m4a/m4a.c:EWRAM_DATA void *gMPlayJumpTable[36] = {};

[JaceCear]

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