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

This applies the change made to libunwind+libcxxabi+libcxx in D113253
to compiler-rt as well.

Differential Revision: https://reviews.llvm.org/D115674

Author: petrhosek

compiler-rt/CMakeLists.txt

@@ -506,6 +506,11 @@ 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

@@ -4,9 +4,22 @@ 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)