Revert "[CMake] Use LLVM_TARGET_TRIPLE in runtimes"

This reverts commit bec8a372fc0db95852748691c0f4933044026b25.

This causes many of these errors to appear when rebuilding runtimes part
of fuchsia's toolchain:

ld.lld: error:
/usr/local/google/home/paulkirth/llvm-upstream/build/lib/x86_64-unknown-linux-gnu/libunwind.a(libunwind.cpp.o)
is incompatible with elf64-x86-64

This can be reproduced by making a complete toolchain, saving any source
file with no changes, then rerunning ninja distribution.

NOKEYCHECK=True
GitOrigin-RevId: 96d63993dd3698bbf2d6a83c035cd05faed7317b
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a626af6..5c54788 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -115,8 +115,8 @@
 set(LIBUNWIND_STATIC_OUTPUT_NAME "unwind" CACHE STRING "Output name for the static libunwind runtime library.")
 
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
-  set(LIBUNWIND_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_TARGET_TRIPLE})
-  set(LIBUNWIND_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_TARGET_TRIPLE} CACHE PATH
+  set(LIBUNWIND_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
+  set(LIBUNWIND_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
       "Path where built libunwind libraries should be installed.")
   if(LIBCXX_LIBDIR_SUBDIR)
     string(APPEND LIBUNWIND_LIBRARY_DIR /${LIBUNWIND_LIBDIR_SUBDIR})
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index aa5f92f..0a09553 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -29,7 +29,7 @@
 if (CMAKE_CXX_COMPILER_TARGET)
   serialize_lit_param(target_triple "\"${CMAKE_CXX_COMPILER_TARGET}\"")
 else()
-  serialize_lit_param(target_triple "\"${LLVM_TARGET_TRIPLE}\"")
+  serialize_lit_param(target_triple "\"${LLVM_DEFAULT_TARGET_TRIPLE}\"")
 endif()
 
 foreach(param IN LISTS LIBUNWIND_TEST_PARAMS)