Tests/RunCMake/IAR: Simplify test project cmake code

Tests/RunCMake/IAR/iar-asm.cmake

 enable_language(ASM)
 
-add_executable(exec-asm)
-target_sources(exec-asm PRIVATE module.asm)
+add_executable(exec-asm module.asm)
 target_link_options(exec-asm PRIVATE ${LINKER_OPTS})

Tests/RunCMake/IAR/iar-c.cmake

 enable_language(C)
 
-add_executable(exec-c)
-target_sources(exec-c PRIVATE module.c)
+add_executable(exec-c module.c)
 target_link_options(exec-c PRIVATE ${LINKER_OPTS})

Tests/RunCMake/IAR/iar-cxx.cmake

 enable_language(CXX)
 
-add_executable(exec-cxx)
-target_sources(exec-cxx PRIVATE module.cxx)
+add_executable(exec-cxx module.cxx)
 target_link_options(exec-cxx PRIVATE ${LINKER_OPTS})

Tests/RunCMake/IAR/iar-lib.cmake

 enable_language(C)
 
-add_library(iar-test-lib)
-target_sources(iar-test-lib PRIVATE libmod.c)
+add_library(iar-test-lib libmod.c)
 
-add_executable(exec-lib-c)
-target_sources(exec-lib-c PRIVATE module.c)
+add_executable(exec-lib-c module.c)
 target_compile_definitions(exec-lib-c PRIVATE __USE_LIBFUN)
-target_link_libraries(exec-lib-c LINK_PUBLIC iar-test-lib)
+target_link_libraries(exec-lib-c PRIVATE iar-test-lib)
 target_link_options(exec-lib-c PRIVATE ${LINKER_OPTS})