fix cmake version for tests

README.md

@@ -37,7 +37,7 @@ Home page for json-c: https://github.com/json-c/json-c/wiki
 
  - `gcc`, `clang`, or another C compiler
 
- - `cmake>=2.8`, `>=3.16` recommended
+ - `cmake>=2.8`, `>=3.16` recommended, `cmake=>3.1` for tests
 
 To generate docs you'll also need:
  - `doxygen>=1.8.13`

tests/CMakeLists.txt

@@ -1,4 +1,4 @@
-
+cmake_minimum_required(VERSION 3.1)
 add_executable(test1Formatted test1.c parse_flags.c parse_flags.h)
 target_compile_definitions(test1Formatted PRIVATE TEST_FORMATTED=1)
 target_link_libraries(test1Formatted PRIVATE ${PROJECT_NAME})