sim: Fix linker support and macOS host build issues

Update SIM configuration and CMake toolchain to resolve
linker errors when building on macOS. Adjust POSIX host
implementation to ensure successful compilation and
proper behavior of the sim target.

Modified:
- arch/sim/Kconfig
- arch/sim/src/cmake/Toolchain.cmake
- arch/sim/src/sim/posix/sim_hostmisc.c

Signed-off-by: Aditya Yadav <166515021+aditya0yadav@users.noreply.github.com>

arch/sim/Kconfig

@@ -37,6 +37,7 @@ config ARCH_CHIP
 
 choice
 	prompt "Toolchain Selection"
+	default SIM_TOOLCHAIN_CLANG if HOST_MACOS
 	default SIM_TOOLCHAIN_GCC
 
 config SIM_TOOLCHAIN_GCC

arch/sim/src/cmake/Toolchain.cmake

@@ -20,7 +20,7 @@
 #
 # ##############################################################################
 
-if(APPLE)
+if(APPLE AND CONFIG_SIM_TOOLCHAIN_GCC)
   find_program(CMAKE_C_ELF_COMPILER x86_64-elf-gcc)
   find_program(CMAKE_CXX_ELF_COMPILER x86_64-elf-g++)
 endif()
@@ -121,7 +121,12 @@ if(CONFIG_STACK_USAGE_WARNING)
 endif()
 
 if(CONFIG_COVERAGE_ALL)
-  add_compile_options(-fprofile-arcs -ftest-coverage -fno-inline)
+  if(CONFIG_ARCH_TOOLCHAIN_GCC)
+    add_compile_options(-fprofile-arcs -ftest-coverage -fno-inline)
+  elseif(CONFIG_ARCH_TOOLCHAIN_CLANG)
+    add_compile_options(-fprofile-instr-generate -fcoverage-mapping)
+    add_link_options(-fprofile-instr-generate)
+  endif()
 endif()
 
 if(CONFIG_PROFILE_ALL OR CONFIG_SIM_PROFILE)

arch/sim/src/sim/posix/sim_hostmisc.c

@@ -24,6 +24,7 @@
  * Included Files
  ****************************************************************************/
 
+#include <signal.h>
 #include <errno.h>
 #include <limits.h>
 #include <stdio.h>