Reserve enclave memory in embedded enclave
Reserve enclave memory in embedded enclave

Currently embedded loader maps file before loading the enclave, if the
enclave base address is specified it could be used and failed to load
the enclave in the expected address. This commit reserves the memory to
load the enclave while embedded loader is doing file mapping.

PiperOrigin-RevId: 246350105
Change-Id: Ia9d0fee48ac8c5961d108c4e2dde9a69fda4107c

google/asylo,google/asylo,google/asylo,google/asylo,google/asylo,google/asylo