Fix cmakelint issues

Expression repeated inside endif; better to use only endif()
 [readability/logic]  
Extra spaces between 'if' and its () [whitespace/extra]  
Do not mix upper and lower case commands [readability/mixedcase]  
Weird indentation; use 2 spaces [whitespace/indent]  
Mismatching spaces inside () after command [whitespace/mismatch]  
Extra spaces between 'set' and its () [whitespace/extra]