[CMake] Remove variable reference that isn't used.

[cdavis5x]

Summary

This variable is never defined, so its value is always empty. Since
libunwind is needed to build the C++ ABI library in the first place,
it should never be linked to the C++ ABI library anyway.

[mstorsjo]

src/CMakeLists.txt

54

Is there any point in this line at all now, or can it be removed altogether?

[cdavis5x]

src/CMakeLists.txt

54

I think list(APPEND) can fail if the variable doesn't exist.

[mstorsjo]

src/CMakeLists.txt

54

Okay - after reading the cmake docs, I agree that this seems to be the correct solution.

src/CMakeLists.txt

 endif()
 
 set(LIBUNWIND_SOURCES
     ${LIBUNWIND_CXX_SOURCES}
     ${LIBUNWIND_C_SOURCES}
     ${LIBUNWIND_ASM_SOURCES})
 
 # Generate library list.
-set(libraries ${LIBUNWINDCXX_ABI_LIBRARIES})
+set(libraries)
 append_if(libraries LIBUNWIND_HAS_C_LIB c)
 append_if(libraries LIBUNWIND_HAS_GCC_S_LIB gcc_s)
 append_if(libraries LIBUNWIND_HAS_DL_LIB dl)
 if (LIBUNWIND_ENABLE_THREADS)
   append_if(libraries LIBUNWIND_HAS_PTHREAD_LIB pthread)
 endif()
 
 # Setup flags.