Revert "[runtime] Build compiler-rt with --unwindlib=none"

This reverts commit 102bc63 because
some tests are failing on sanitizer bots.

Author: petrhosek

compiler-rt/CMakeLists.txt

@@ -506,11 +506,6 @@ list(APPEND COMPILER_RT_COMMON_LINK_FLAGS ${stdlib_flag})
 
 macro(append_libcxx_libs var)
   if (${var}_INTREE)
-    # If we're linking directly against the libunwind that we're building
-    # in the same invocation, don't try to link in the toolchain's
-    # default libunwind (which may be missing still).
-    append_list_if(CXX_SUPPORTS_UNWINDLIB_NONE_FLAG --unwindlib=none SANITIZER_COMMON_LINK_FLAGS)
-
     if (SANITIZER_USE_STATIC_LLVM_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))
       list(APPEND ${var}_LIBRARIES unwind_static)
     elseif (TARGET unwind_shared OR HAVE_LIBUNWIND)

compiler-rt/cmake/config-ix.cmake

@@ -4,22 +4,9 @@ include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckIncludeFiles)
 include(CheckLibraryExists)
-include(LLVMCheckCompilerLinkerFlag)
 include(CheckSymbolExists)
 include(TestBigEndian)
 
-# The compiler driver may be implicitly trying to link against libunwind.
-# This is normally ok (libcxx relies on an unwinder), but if libunwind is
-# built in the same cmake invocation as compiler-rt and we're using the
-# in tree version of runtimes, we'd be linking against the just-built
-# libunwind (and the compiler implicit -lunwind wouldn't succeed as the newly
-# built libunwind isn't installed yet). For those cases, it'd be good to
-# link with --uwnindlib=none. Check if that option works.
-llvm_check_compiler_linker_flag(C "--unwindlib=none" CXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
-if (CXX_SUPPORTS_UNWINDLIB_NONE_FLAG)
-  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --unwindlib=none")
-endif()
-
 check_library_exists(c fopen "" COMPILER_RT_HAS_LIBC)
 if (COMPILER_RT_USE_BUILTINS_LIBRARY)
   include(HandleCompilerRT)