[libc++abi] Introduce a LIBCXXABI_LIBRARY_VERSION option

That option controls the 'VERSION' attribute of the libc++abi shared
library, which in turn controls the name of the actual dylib being

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@373949 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8ca1690..fafb777 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -77,6 +77,11 @@
 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.")
+"Version of libc++abi. This will be reflected in the name of the shared \
+library produced. For example, -DLIBCXXABI_LIBRARY_VERSION=x.y will \
+result in the library being named libc++abi.x.y.dylib, along with the \
+usual symlinks pointing to that.")
 # 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
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0bb164d..b38973b 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -176,7 +176,7 @@
-                            "1.0"
+                            "${LIBCXXABI_LIBRARY_VERSION}"