[symbolizer] Check if dependecy exist

Deppending on how we build compiler-rt, as a project,
or as runtime, tools needed to build can be prebuilt or
exist as a target.

Author: vitalybuka

compiler-rt/lib/sanitizer_common/symbolizer/CMakeLists.txt

@@ -6,9 +6,15 @@ foreach(arch ${SANITIZER_COMMON_SUPPORTED_ARCH})
   add_custom_command(OUTPUT ${RTSanitizerCommonSymbolizerInternalDir}
                      COMMAND ${CMAKE_COMMAND} -E make_directory ${RTSanitizerCommonSymbolizerInternalDir})
 
+  foreach(dep clang lld llvm-tblgen opt llvm-ar llvm-link llvm-ranlib llvm-symbolizer)
+    if (TARGET ${dep})
+      list(APPEND SYMBOLIZER_DEPS ${dep})
+    endif()
+  endforeach()
+
   add_custom_command(OUTPUT RTSanitizerCommonSymbolizerInternal.${arch}.o
                      DEPENDS ${RTSanitizerCommonSymbolizerInternalDir} 
-                             clang lld llvm-tblgen opt llvm-ar llvm-link llvm-ranlib llvm-symbolizer
+                             ${SYMBOLIZER_DEPS}
                              sanitizer_wrappers.cpp
                              sanitizer_symbolize.cpp
                              scripts/build_symbolizer.sh