[compiler-rt] Set the ZX_VMO_RESIZABLE option for zx_vmo_create

Currently VMO in Zircon create using the zx_vmo_create is resizable
by default, but we'll be changing this in the future, requiring an
explicit flag to make the VMO resizable.

Prepare for this change by passing ZX_VMO_RESIZABLE option to all
zx_vmo_create calls that need resizable VMO.

Differential Revision: https://reviews.llvm.org/D61450

llvm-svn: 359803