If Mesa is executed under valgrind, fd_bo_init_common() calls
fd_bo_map() internally. For the heap (sub-block) allocator this causes a
segfault in fd_bo_map(), when this function tries to call the offset()
callback.
To prevent this from happening, preallocate fb->map before calling into
fd_bo_init_common(), stop calling VG_BO_ALLOC() if the memory map is
already initialised and disable the VG_BO_FREE call for the heap
allocator.
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26277>