sys-libs/libcxx/files/libcxx-9-use-libgcc_eh.patch

Link libcxx with gcc_eh when linking with gcc_s is
not desired. Normally, llvm's libunwind would be used but
we are not using libunwind in ChromeOS right now because of
some reported crashes when libunwind was used.
https://crbug.com/747113

diff --git a/libcxx/cmake/config-ix.cmake b/libcxx/cmake/config-ix.cmake
index 23ae71025e5..6820970c616 100644
--- a/libcxx/cmake/config-ix.cmake
+++ b/libcxx/cmake/config-ix.cmake
@@ -27,7 +27,7 @@ endif()
 # configuration checks to avoid spurious link errors.
 check_c_compiler_flag(-nodefaultlibs LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
 if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
-  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nostdlib++")
   if (LIBCXX_HAS_C_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES c)
   endif ()
diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 4f6e2b4aa62..0706cc46182 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -136,7 +136,7 @@ if (APPLE AND LLVM_USE_SANITIZER)
 endif()
 
 function(cxx_link_system_libraries target)
-  target_add_link_flags_if_supported(${target} PRIVATE "-nodefaultlibs")
+  target_add_link_flags_if_supported(${target} PRIVATE "-nostdlib++")
   target_add_compile_flags_if_supported(${target} PRIVATE "/Zl")
   target_add_link_flags_if_supported(${target} PRIVATE "/nodefaultlib")
 
@@ -161,10 +161,7 @@ function(cxx_link_system_libraries target)
   endif()
 
   if (LIBCXX_USE_COMPILER_RT)
-    find_compiler_rt_library(builtins LIBCXX_BUILTINS_LIBRARY)
-    if (LIBCXX_BUILTINS_LIBRARY)
-      target_link_libraries(${target} PUBLIC "${LIBCXX_BUILTINS_LIBRARY}")
-    endif()
+    add_link_flags("-rtlib=compiler-rt")
   elseif (LIBCXX_HAS_GCC_S_LIB)
     target_link_libraries(${target} PUBLIC gcc_s)
   endif()
@@ -255,6 +256,8 @@ if (LIBCXX_ENABLE_SHARED)
       target_link_libraries(cxx_shared PRIVATE unwind)
       list(APPEND LIBCXX_INTERFACE_LIBRARIES unwind) # For the linker script
     endif()
+  elseif (NOT LIBCXX_HAS_GCC_S_LIB)
+      add_library_flags(gcc_eh)
   endif()
 
   # Link against libc++abi