Fix syntax error in recent CMake change.

llvm-svn: 280042
diff --git a/libcxx/lib/CMakeLists.txt b/libcxx/lib/CMakeLists.txt
index 3abfd78..e6f9ff6 100644
--- a/libcxx/lib/CMakeLists.txt
+++ b/libcxx/lib/CMakeLists.txt
@@ -106,7 +106,7 @@
       "/usr/lib/libSystem.B.dylib")
   else()
     if (DEFINED CMAKE_OSX_SYSROOT)
-      list(FIND ${CMAKE_OSX_ARCHITECTURES} "armv7" OSX_HAS_ARMV7)
+      list(FIND CMAKE_OSX_ARCHITECTURES "armv7" OSX_HAS_ARMV7)
       if (NOT OSX_HAS_ARMV7 EQUAL -1)
         set(OSX_RE_EXPORT_LINE
           "${CMAKE_OSX_SYSROOT}/usr/lib/libc++abi.dylib"