[cmake] [libcxxabi] Don't print warning when tests are disabled.

[hintonda]

Summary

Don't print, possibly erroneous, warning if
LIBCXXABI_INCLUDE_TESTS is false.

This patch fixes a problem introduced in r291367.

CMakeLists.txt

if (NOT LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL STREQUAL "")
     include_directories("${LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL}")
   endif()
 endif()
 
 # Add source code. This also contains all of the logic for deciding linker flags
 # soname, etc...
 add_subdirectory(src)
 
-if (NOT LIBCXXABI_INCLUDE_TESTS OR (LIBCXXABI_STANDALONE_BUILD AND NOT LIBCXXABI_ENABLE_SHARED))
-  # We can't reasonably test the system C++ library with a static libc++abi.
-  # We either need to be able to replace libc++abi at run time (with a shared
-  # libc++abi), or we need to be able to replace the C++ runtime (with a non-
-  # standalone build).
-  message(WARNING "The libc++abi tests aren't valid when libc++abi is built "
-                  "standalone (i.e. outside of llvm/projects/libcxxabi ) and "
-                  "is built without a shared library.  Either build a shared "
-                  "library, build libc++abi at the same time as you build "
-                  "libc++, or do without testing.  No check target will be "
-                  "available!")
+if (LIBCXXABI_INCLUDE_TESTS)
+  if (LIBCXXABI_STANDALONE_BUILD AND NOT LIBCXXABI_ENABLE_SHARED)
+    # We can't reasonably test the system C++ library with a static
+    # libc++abi.  We either need to be able to replace libc++abi at
+    # run time (with a shared libc++abi), or we need to be able to
+    # replace the C++ runtime (with a non- standalone build).
+    message(WARNING "The libc++abi tests aren't valid when libc++abi "
+                    "is built standalone (i.e. outside of "
+                    "llvm/projects/libcxxabi ) and is built without "
+                    "a shared library.  Either build a shared "
+                    "library, build libc++abi at the same time as "
+                    "you build libc++, or do without testing.  No "
+                    "check target will be available!")
   else()
     add_subdirectory(test)
     add_subdirectory(fuzz)
   endif()
+endif()