Merge pull request #90 from njwhite/master

don't override CMAKE_INSTALL_PREFIX if specified

Author: artwyman

CMakeLists.txt

@@ -8,7 +8,9 @@ option(JSON11_ENABLE_DR1467_CANARY "Enable canary test for DR 1467" OFF)
 
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_INSTALL_PREFIX /usr)
+if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+ set(CMAKE_INSTALL_PREFIX /usr)
+endif()
 
 add_library(json11 json11.cpp)
 target_include_directories(json11 PUBLIC ${CMAKE_SOURCE_DIR})