Prevent cmakelint warnings

You may install https://pypi.org/project/cmakelint/



```shell

bash-5.0$ find . -name CMakeLists.txt | xargs cmakelint

./example/CMakeLists.txt:5: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:6: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:7: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:8: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:9: Weird indentation; use 2 spaces [whitespace/indent]

./example/CMakeLists.txt:14: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:15: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:15: Line ends in whitespace [whitespace/eol]

./example/CMakeLists.txt:16: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:17: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:18: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:19: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:20: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:23: Extra spaces between 'foreach' and its () [whitespace/extra]

./example/CMakeLists.txt:24: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:25: Tab found; please use spaces [whitespace/tabs]

./example/CMakeLists.txt:26: Tab found; please use spaces [whitespace/tabs]

./src/jsontestrunner/CMakeLists.txt:3: Extra spaces between 'find_package' and its () [whitespace/extra]

./src/jsontestrunner/CMakeLists.txt:13: Weird indentation; use 2 spaces [whitespace/indent]

./src/jsontestrunner/CMakeLists.txt:14: Weird indentation; use 2 spaces [whitespace/indent]

./src/jsontestrunner/CMakeLists.txt:42: Weird indentation; use 2 spaces [whitespace/indent]

./src/jsontestrunner/CMakeLists.txt:43: Weird indentation; use 2 spaces [whitespace/indent]

./src/jsontestrunner/CMakeLists.txt:46: Weird indentation; use 2 spaces [whitespace/indent]

./src/jsontestrunner/CMakeLists.txt:47: Weird indentation; use 2 spaces [whitespace/indent]

./src/lib_json/CMakeLists.txt:4: Weird indentation; use 2 spaces [whitespace/indent]

./src/lib_json/CMakeLists.txt:10: Expression repeated inside endif; better to use only endif() [readability/logic]

./src/lib_json/CMakeLists.txt:46: Mismatching spaces inside () after command [whitespace/mismatch]

./src/lib_json/CMakeLists.txt:69: Expression repeated inside else; better to use only else() [readability/logic]

./src/lib_json/CMakeLists.txt:84: Mismatching spaces inside () after command [whitespace/mismatch]

./src/lib_json/CMakeLists.txt:87: Mismatching spaces inside () after command [whitespace/mismatch]

./src/lib_json/CMakeLists.txt:144: Mismatching spaces inside () after command [whitespace/mismatch]

./src/lib_json/CMakeLists.txt:150: Mismatching spaces inside () after command [whitespace/mismatch]

./src/test_lib_json/CMakeLists.txt:3: Mismatching spaces inside () after command [whitespace/mismatch]

./src/test_lib_json/CMakeLists.txt:30: Mismatching spaces inside () after command [whitespace/mismatch]

./src/test_lib_json/CMakeLists.txt:34: Expression repeated inside else; better to use only else() [readability/logic]

./src/test_lib_json/CMakeLists.txt:36: Mismatching spaces inside () after command [whitespace/mismatch]

./src/test_lib_json/CMakeLists.txt:42: Weird indentation; use 2 spaces [whitespace/indent]

Total Errors: 37

bash-5.0$ 

```

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