[libunwind][CMake] Provide option to disable instalation of the library

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

This change also adds the install-unwind target for consistency with the
libcxxabi and libcxx CMake build.

Differential Revision: https://reviews.llvm.org/D40195

git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@318569 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/CMakeLists.txt b/CMakeLists.txt
index eef7479..dda2799 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt

@@ -135,6 +135,7 @@
 
 set(LIBUNWIND_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
     "Define suffix of library directory name (32/64)")
+option(LIBUNWIND_INSTALL_LIBRARY "Install the libunwind library." ON)
 set(LIBUNWIND_TARGET_TRIPLE "" CACHE STRING "Target triple for cross compiling.")
 set(LIBUNWIND_GCC_TOOLCHAIN "" CACHE PATH "GCC toolchain for cross compiling.")
 set(LIBUNWIND_SYSROOT "" CACHE PATH "Sysroot for cross compiling.")

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 17550d9..700b52e 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt

@@ -132,7 +132,16 @@
 # Add a meta-target for both libraries.
 add_custom_target(unwind DEPENDS ${LIBUNWIND_TARGETS})
 
-install(TARGETS ${LIBUNWIND_TARGETS}
-  LIBRARY DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LIBUNWIND_LIBDIR_SUFFIX}
-  ARCHIVE DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LIBUNWIND_LIBDIR_SUFFIX})
+if (LIBUNWIND_INSTALL_LIBRARY)
+  install(TARGETS ${LIBUNWIND_TARGETS}
+    LIBRARY DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LIBUNWIND_LIBDIR_SUFFIX} COMPONENT unwind
+    ARCHIVE DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LIBUNWIND_LIBDIR_SUFFIX} COMPONENT unwind)
+endif()
 
+if (NOT CMAKE_CONFIGURATION_TYPES AND LIBUNWIND_INSTALL_LIBRARY)
+  add_custom_target(install-unwind
+    DEPENDS unwind
+    COMMAND "${CMAKE_COMMAND}"
+            -DCMAKE_INSTALL_COMPONENT=unwind
+            -P "${LIBCXXABI_BINARY_DIR}/cmake_install.cmake")
+endif()