build: update the min cmake version to 3.20

The cmake versions < 3.20 do not work anymore with the changes done
to the build system for the EL0 app framework. The workarounds for
supporting version < 3.20 are not trivial and is introducing some
complexity into the build. Hence bumping up the min required version
for cmake to 3.20.


Change-Id: I8c2121f9b11d33f5c6ffc8bb7752039f4175f509
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
2 files changed