[libc++abi] Add install-cxxabi-stripped target

LLVM is gaining install-*-stripped targets to perform stripped installs,
and in order for this to be useful for install-distribution, all
potential distribution components should have stripped installation
targets. LLVM has a function to create these install targets, but since
we can't use LLVM CMake functions in libc++abi, let's do it manually.

Differential Revision: https://reviews.llvm.org/D40681

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@319499 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 32e04c8..240f6d0 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -192,6 +192,12 @@
     COMMAND "${CMAKE_COMMAND}"
             -DCMAKE_INSTALL_COMPONENT=cxxabi
             -P "${LIBCXXABI_BINARY_DIR}/cmake_install.cmake")
+  add_custom_target(install-cxxabi-stripped
+    DEPENDS cxxabi
+    COMMAND "${CMAKE_COMMAND}"
+            -DCMAKE_INSTALL_COMPONENT=cxxabi
+            -DCMAKE_INSTALL_DO_STRIP=1
+            -P "${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)