[compiler-rt] Make use of undefined symbols configurable

We want to disable the use of undefined symbols on Fuchsia, but there
are cases where it might be desirable so may it configurable.

Differential Revision: https://reviews.llvm.org/D104728

diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
index 5d0e617..24018ca 100644 (file)
--- a/compiler-rt/CMakeLists.txt
+++ b/compiler-rt/CMakeLists.txt
@@ -437,10 +437,18 @@ else()
 endif()
 
 append_list_if(COMPILER_RT_HAS_LIBC c SANITIZER_COMMON_LINK_LIBS)
+if("${CMAKE_SYSTEM_NAME}" STREQUAL "Fuchsia")
+  list(APPEND SANITIZER_COMMON_LINK_LIBS zircon)
+endif()
 
 if("${CMAKE_SYSTEM_NAME}" STREQUAL "Fuchsia")
+  set(SANITIZER_NO_UNDEFINED_SYMBOLS_DEFAULT ON)
+else()
+  set(SANITIZER_NO_UNDEFINED_SYMBOLS_DEFAULT OFF)
+endif
+option(SANITIZER_NO_UNDEFINED_SYMBOLS ${SANITIZER_NO_UNDEFINED_SYMBOLS_DEFAULT})
+if (SANITIZER_NO_UNDEFINED_SYMBOLS)
   list(APPEND SANITIZER_COMMON_LINK_FLAGS -Wl,-z,defs)
-  list(APPEND SANITIZER_COMMON_LINK_LIBS zircon)
 endif()
 
 # TODO: COMPILER_RT_COMMON_CFLAGS and COMPILER_RT_COMMON_LINK_FLAGS are