[clang-shlib] Don't link with static clang libraries

[tstellar]

Summary

If we are building static libraries we don't need to link them into
clang-shlib, since clang-shlib already has all the individual object
files linked in.

[smeenai]

LGTM

clang/tools/clang-shlib/CMakeLists.txt

 # Building libclang-cpp.so fails if LLVM_ENABLE_PIC=Off
 if (NOT LLVM_ENABLE_PIC)
   return()
 endif()
 
 get_property(clang_libs GLOBAL PROPERTY CLANG_STATIC_LIBS)
 
 foreach (lib ${clang_libs})
   if(XCODE)
     # Xcode doesn't support object libraries, so we have to trick it into
     # linking the static libraries instead.
     list(APPEND _DEPS "-force_load" ${lib})
   else()
     list(APPEND _OBJECTS $<TARGET_OBJECTS:obj.${lib}>)
   endif()
+  if (BUILD_SHARED_LIBS)
+    # If we are building static libraries, then we don't need to add the static
+    # libraries as a depedency, because we are already linking against the
+    # individual object files.
     list(APPEND _DEPS $<TARGET_PROPERTY:${lib},INTERFACE_LINK_LIBRARIES>)
+  endif()
 
   # clang libraries are redundant since we are linking all the individual
   # object files into libclang-cpp.so, so filter them out from _DEPS.
   # This avoids problems with LLVM global data when building with
   # BUILD_SHARED_LIBS=ON
   # FIXME: We could use list(FILTER) with cmake >= 3.6
   # FIXME: With cmake >= 3.15 we could use the generator expression
   # $<FILTER:list,INCLUDE|EXCLUDE,regex>