install-deps.sh: add option to skip prebuilt boost-* pkgs installation
Prebuilt boost-1.67 packages are only available for limited arch on Ubuntu
(x86_64 for bionic, x86_64 and arm64 for xenial). This will cause install
failure on missing platforms.
Add a new env variable to allow user to build and install from source
while the default option is to install pkgs from ceph repo.
Change-Id: I4259733dd40a638d1bd5d1578a64ecaaa6490121 Signed-off-by: Jun He <jun.he@arm.com>