fix(lib/debug): Fix LOG_LEVEL for Multi-Config build

The CMAKE_BUILD_TYPE variable is invalid for Multi-Config builds.
The previous implementation depended on this to set the default
LOG_LEVEL for Debug and Release builds. This is now corrected to
an implementation which is compatible with Multi-Config build
generators.

fixes TF-RMM/tf-rmm#16

Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Change-Id: I53a2d850b532ad169c09e0eeed4c485752be8a7a
3 files changed