libroot: malloc() can't allocate more then 1063315264 bytes

[X512]

This is hrev55275.

Problem code: ​https://git.haiku-os.org/haiku/tree/src/system/libroot/posix/malloc_hoard2/threadheap.cpp#n48.

Causing icu66 build failure on riscv64.

[waddlesplash]

Why does ICU allocate 1GB during the build, anyway?

We really need to replace hoard2, but musl's malloc has those performance issues ... possibly I should look into patching it a bit more.

[pulkomandy]

It looks like if you set MAX_INTERNAL_FRAGMENTATION to 10, you can get up to 2GB. Good enough until we replace the allocator?