[libcxxabi] Include flag to exclude test and fuzz subdirs.

[bryant]

Summary

LLVM_INCLUDE_TESTS
CLANG_INCLUDE_TESTS
LIBCXX_INCLUDE_TESTS

...and now this.

[bryant]

set default val to LLVM_INCLUDE_TESTS, like the others.

libcxxabi/trunk/CMakeLists.txt

 option(LIBCXXABI_USE_LLVM_UNWINDER "Build and use the LLVM unwinder." OFF)
 option(LIBCXXABI_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
 option(LIBCXXABI_ENABLE_THREADS "Build with threads enabled" ON)
 option(LIBCXXABI_HAS_PTHREAD_API "Ignore auto-detection and force use of pthread API" OFF)
 option(LIBCXXABI_HAS_EXTERNAL_THREAD_API
   "Build libc++abi with an externalized threading API.
   This option may only be set to ON when LIBCXXABI_ENABLE_THREADS=ON." OFF)
 option(LIBCXXABI_BUILD_32_BITS "Build 32 bit libc++abi." ${LLVM_BUILD_32_BITS})
+option(LIBCXXABI_INCLUDE_TESTS "Generate build targets for the libc++abi unit tests." ${LLVM_INCLUDE_TESTS})
 set(LIBCXXABI_TARGET_TRIPLE "" CACHE STRING "Target triple for cross compiling.")
 set(LIBCXXABI_GCC_TOOLCHAIN "" CACHE PATH "GCC toolchain for cross compiling.")
 set(LIBCXXABI_SYSROOT "" CACHE PATH "Sysroot for cross compiling.")
 set(LIBCXXABI_LIBCXX_LIBRARY_PATH "" CACHE PATH "The path to libc++ library.")
 
 # Default to building a shared library so that the default options still test
 # the libc++abi that is being built. There are two problems with testing a
 # static libc++abi. In the case of a standalone build, the tests will link the
if (LIBCXXABI_USE_LLVM_UNWINDER OR LLVM_NATIVE_ARCH MATCHES ARM)
   include_directories("${LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL}")
   include_directories("${LIBCXXABI_LIBUNWIND_SOURCES}")
 endif()
 
 # Add source code. This also contains all of the logic for deciding linker flags
 # soname, etc...
 add_subdirectory(src)
 
-if (LIBCXXABI_STANDALONE_BUILD AND NOT LIBCXXABI_ENABLE_SHARED)
+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!")
 else()
   add_subdirectory(test)
   add_subdirectory(fuzz)
 endif()