Haiku patches have been sent upstream and have been included in this release so it builds out of the box. Only problem still is with two asm files in:

scummvm/trunk/graphics/scaler/

Offending files are:

hq2x_i386.asm hq3x_i386.asm

At the bottom of those 2 files you find the lines:

    %ifidn __OUTPUT_FORMAT__,elf
    section .note.GNU-stack noalloc noexec nowrite progbits
    %endif

These lines add an extra header GNU_STACK to the binary that Haiku can't handle (yet?) so it's safe to remove them.

Then just run ./configure --prefix, make and make install.