While porting TF-M to the IAR toolchain I ran into a number of issues with the required tools and packages necessary for building TF-M.
IAR requires cmake 3.15 or later for building on linux. 3.14 works when building on windows.
The problem appears to be that the IAR tools have an ".exe" file extension in 3.14 and older, causing the linux version of the tools not to be found.
Apparently ARMCLANG does not work with cmake 3.15 or higher, and this needs to be sorted out.
GNUARM works fine with either.
The version required with TF-M, 3.0.1, has a CMakeLists.txt file that doesn't work with IAR. The current development version, which appears to be version based on 3.1.0, has a fix for this, but it doesn't work with TF-M .
Versions older than 5.7.0 does not work with V8M targets with IAR due to the non-secure RTX5 libraries having been incorrectly built.