mimalloc3 wasi target fails to compile

I get the compilation errors when I try to build `mimalloc3` using `wasi` target.

```
git clone --branch v3.1.5 https://github.com/microsoft/mimalloc.git
```

```
~/w/h/s/h/t/mimalloc ((v3.1.5)) [1]> ~/workspace/build/wasi-sdk-23.0-x86_64-linux/bin/clang src/static.c -I include/ -I src/ --sysroot ~/workspace/build/wasi-sdk-23.0-x86_64-linux/share/wasi-sysroot/
In file included from src/static.c:38:
In file included from src/prim/prim.c:19:
src/prim/wasi/prim.c:92:33: error: call to undeclared function 'mi_align_up_ptr'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
92 | void* aligned_current = mi_align_up_ptr(current, try_alignment); // and align from there to minimize wasted space
| ^
src/prim/wasi/prim.c:92:33: note: did you mean '_mi_align_up_ptr'?
include/mimalloc/internal.h:441:24: note: '_mi_align_up_ptr' declared here
441 | static inline uint8_t* _mi_align_up_ptr(void* p, size_t alignment) {
| ^
In file included from src/static.c:38:
In file included from src/prim/prim.c:19:
src/prim/wasi/prim.c:92:15: error: incompatible integer to pointer conversion initializing 'void *' with an expression of type 'int' [-Wint-conversion]
92 | void* aligned_current = mi_align_up_ptr(current, try_alignment); // and align from there to minimize wasted space
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/prim/wasi/prim.c:101:11: error: call to undeclared function 'mi_align_up_ptr'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
101 | p = mi_align_up_ptr(base, try_alignment);
| ^
src/prim/wasi/prim.c:101:9: error: incompatible integer to pointer conversion assigning to 'void *' from 'int' [-Wint-conversion]
101 | p = mi_align_up_ptr(base, try_alignment);
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4 errors generated.
```

I'm able to get rid of those by `s/mi_align_up_ptr/_mi_align_up_ptr`. I'm happy to create PR if that's what needed to fix it.

Reproduce the failure with the WASI SDK command shown in the issue, then inspect src/prim/wasi/prim.c at lines 92 and 101 and the helper declarations in include/mimalloc/internal.h. Confirm the WASI target builds successfully and that the alignment calls use the declared helper.

Written by the indexing model from the issue text.