Move to CMake 3.20.0.
At the Toolchain WG it was decided to move to CMake 3.20.0.
The main reason for increasing CMake version is better toolchain
support.
Better toolchain support is added in the following CMake versions:
- armclang, CMake 3.15
- Intel oneAPI, CMake 3.20
- IAR, CMake 3.15 and 3.20
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
... because it is (required).
This makes a difference when building with CMake and forgetting
ZEPHYR_BASE or not registering Zephyr in the CMake package registry.
In this particular case, REQUIRED turns this harmless looking log
statement:
-- Could NOT find Zephyr (missing: Zephyr_DIR)
-- The C compiler identification is GNU 9.3.0
-- The CXX compiler identification is GNU 9.3.0
-- Check for working C compiler: /usr/bin/cc
-- ...
-- ...
-- ...
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at CMakeLists.txt:8 (target_sources):
Cannot specify sources for target "app" which is not built by
this project.
... into this louder, clearer, faster and (last but not least) final
error:
CMake Error at CMakeLists.txt:5 (find_package):
Could not find a package configuration file provided by "Zephyr" with
any of the following names:
ZephyrConfig.cmake
zephyr-config.cmake
Add the installation prefix of "Zephyr" to CMAKE_PREFIX_PATH or set
"Zephyr_DIR" to a directory containing one of the above files. If
"Zephyr" provides a separate development package or SDK, be sure it
has been installed.
-- Configuring incomplete, errors occurred!
Signed-off-by: Marc Herbert <marc.herbert@intel.com>
Using find_package to locate Zephyr.
Old behavior was to use $ENV{ZEPHYR_BASE} for inclusion of boiler plate
code.
Whenever an automatic run of CMake happend by the build system / IDE
then it was required that ZEPHYR_BASE was defined.
Using ZEPHYR_BASE only to locate the Zephyr package allows CMake to
cache the base variable and thus allowing subsequent invocation even
if ZEPHYR_BASE is not set in the environment.
It also removes the risk of strange build results if a user switchs
between different Zephyr based project folders and forgetting to reset
ZEPHYR_BASE before running ninja / make.
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
