libunwind: Introduce __libunwind_config.h.

Introduce __libunwind_config.h to avoid cross repository circular
dependency with libcxxabi.

llvm-svn: 242642
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 5191fe9509fab84b7681c7ef6f4eceef877d5339
diff --git a/src/libunwind.cpp b/src/libunwind.cpp
index 8f5078b..9a16e48 100644
--- a/src/libunwind.cpp
+++ b/src/libunwind.cpp
@@ -61,7 +61,7 @@
 #elif defined(__arm64__)
   new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_arm64>(
                                  context, LocalAddressSpace::sThisAddressSpace);
-#elif LIBCXXABI_ARM_EHABI
+#elif _LIBUNWIND_ARM_EHABI
   new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_arm>(
                                  context, LocalAddressSpace::sThisAddressSpace);
 #endif
@@ -205,7 +205,7 @@
 /// Set value of specified float register at cursor position in stack frame.
 _LIBUNWIND_EXPORT int unw_set_fpreg(unw_cursor_t *cursor, unw_regnum_t regNum,
                                     unw_fpreg_t value) {
-#if LIBCXXABI_ARM_EHABI
+#if _LIBUNWIND_ARM_EHABI
   _LIBUNWIND_TRACE_API("unw_set_fpreg(cursor=%p, regNum=%d, value=%llX)\n",
                        static_cast<void *>(cursor), regNum, value);
 #else