Fix cmakelint issues

./src/CMakeLists.txt:1: Mismatching spaces inside () after command [whitespace/mismatch]
./src/CMakeLists.txt:21: Mismatching spaces inside () after command [whitespace/mismatch]
./src/CMakeLists.txt:26: Mismatching spaces inside () after command [whitespace/mismatch]
Total Errors: 3
./CMakeLists.txt:60: Extra spaces between 'if' and its () [whitespace/extra]
./CMakeLists.txt:69: Extra spaces between 'if' and its () [whitespace/extra]
./CMakeLists.txt:86: Mismatching spaces inside () after command [whitespace/mismatch]
./CMakeLists.txt:87: Weird indentation; use 2 spaces [whitespace/indent]
./CMakeLists.txt:91: Mismatching spaces inside () after command [whitespace/mismatch]
Total Errors: 5