[libcxxabi][CMake] Provide option to disable installing of the library

[phosek]

Summary

This is useful in cases where we only build static library and
libc++abi.a is combined with libc++.a into a single archive in which
case we don't want to have libc++abi.a installed separately. The same
option is already provided by libcxx CMake build.

[beanz]

LGTM.

libcxxabi/trunk/CMakeLists.txt

 # has been fixed or worked around the default value should be changed.
 option(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS
     "Build libc++abi with definitions for operator new/delete. Normally libc++
     provides these definitions" ON)
 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." ${LLVM_INCLUDE_TESTS})
 set(LIBCXXABI_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
     "Define suffix of library directory name (32/64)")
+option(LIBCXXABI_INSTALL_LIBRARY "Install the libc++abi library." ON)
 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

libcxxabi/trunk/src/CMakeLists.txt

set_target_properties(cxxabi_static
                           POSITION_INDEPENDENT_CODE
                             ON)
   list(APPEND LIBCXXABI_TARGETS "cxxabi_static")
 endif()
 
 # Add a meta-target for both libraries.
 add_custom_target(cxxabi DEPENDS ${LIBCXXABI_TARGETS})
 
+if (LIBCXXABI_INSTALL_LIBRARY)
   install(TARGETS ${LIBCXXABI_TARGETS}
     LIBRARY DESTINATION ${LIBCXXABI_INSTALL_PREFIX}lib${LIBCXXABI_LIBDIR_SUFFIX} COMPONENT cxxabi
     ARCHIVE DESTINATION ${LIBCXXABI_INSTALL_PREFIX}lib${LIBCXXABI_LIBDIR_SUFFIX} COMPONENT cxxabi
     )
+endif()
 
-if (NOT CMAKE_CONFIGURATION_TYPES)
+if (NOT CMAKE_CONFIGURATION_TYPES AND LIBCXXABI_INSTALL_LIBRARY)
   add_custom_target(install-cxxabi
     DEPENDS cxxabi
     COMMAND "${CMAKE_COMMAND}"
             -DCMAKE_INSTALL_COMPONENT=cxxabi
             -P "${LIBCXXABI_BINARY_DIR}/cmake_install.cmake")
 
   # TODO: This is a legacy target name and should be removed at some point.
   add_custom_target(install-libcxxabi DEPENDS install-cxxabi)
 endif()