[ATFE] Preserve __aeabi_mem* Symbols from compiler-rt when linking with llvm-libc.

Previously, the following symbols were excluded from the build due to the patch introduced in arm#326

__aeabi_memcmp
__aeabi_memset
__aeabi_memcpy
__aeabi_memmove

LLVM libc currently does not provide implementations for __aeabi* symbols. This change ensures that the above implementations from compiler-rt are preserved when linking with llvm-libc , to avoid missing symbol errors at link time.

Author: simpal01

arm-software/embedded/arm-runtimes/CMakeLists.txt

@@ -264,6 +264,12 @@ if(ENABLE_COMPILER_RT_TESTS)
     )
 endif()
 
+if(NOT C_LIBRARY STREQUAL "llvmlibc")
+    set(compiler_rt_cmake_args
+    -DCOMPILER_RT_EXCLUDE_LIBC_PROVIDED_ARM_AEABI_BUILTINS=ON
+  )
+endif()
+
 ExternalProject_Add(
     compiler_rt
     SOURCE_DIR ${llvmproject_src_dir}/compiler-rt
@@ -290,13 +296,13 @@ ExternalProject_Add(
     -DCMAKE_RANLIB=${LLVM_BINARY_DIR}/bin/llvm-ranlib${CMAKE_EXECUTABLE_SUFFIX}
     -DCMAKE_SYSTEM_NAME=Generic
     -DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY
+    ${compiler_rt_cmake_args}
     -DCOMPILER_RT_BAREMETAL_BUILD=ON
     -DCOMPILER_RT_BUILD_LIBFUZZER=OFF
     -DCOMPILER_RT_BUILD_PROFILE=OFF
     -DCOMPILER_RT_BUILD_SANITIZERS=OFF
     -DCOMPILER_RT_BUILD_XRAY=OFF
     -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
-    -DCOMPILER_RT_EXCLUDE_LIBC_PROVIDED_ARM_AEABI_BUILTINS=ON
     -DLLVM_CMAKE_DIR=${LLVM_BINARY_DIR}
     -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
     ${compiler_rt_test_cmake_args}