Fix SOVERSION of shared library

Fixes #1434
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 7081312..8f471ea 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -22,7 +22,7 @@
 set_target_properties(benchmark PROPERTIES
   OUTPUT_NAME "benchmark"
   VERSION ${GENERIC_LIB_VERSION}
-  SOVERSION 2
+  SOVERSION ${GENERIC_LIB_SOVERSION}
 )
 target_include_directories(benchmark PUBLIC
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>