Revert "Use ."

This reverts commit d60cf93.

Author: DanielCChen

libunwind/CMakeLists.txt

@@ -140,7 +140,7 @@ set(LIBUNWIND_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE STRING
 set(LIBUNWIND_SHARED_OUTPUT_NAME "unwind" CACHE STRING "Output name for the shared libunwind runtime library.")
 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 NOT ${CMAKE_SYSTEM_NAME} MATCHES "AIX")
+if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE NOT CMAKE_SYSTEM_NAME MATCHES "AIX")
   set(LIBUNWIND_TARGET_SUBDIR ${LLVM_DEFAULT_TARGET_TRIPLE})
   if(LIBUNWIND_LIBDIR_SUBDIR)
     string(APPEND LIBUNWIND_TARGET_SUBDIR /${LIBUNWIND_LIBDIR_SUBDIR})