Merge pull request #4 from facebook/dev

merge

build/cmake/lib/CMakeLists.txt

@@ -194,10 +194,12 @@ if (ZSTD_BUILD_STATIC)
 endif ()
 
 # uninstall target
-configure_file(
-        "${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake.in"
-        "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake"
-        IMMEDIATE @ONLY)
+if (NOT TARGET uninstall)
+    configure_file(
+            "${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake.in"
+            "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake"
+            IMMEDIATE @ONLY)
 
-add_custom_target(uninstall
-        COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
+    add_custom_target(uninstall
+            COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
+endif ()