Fix cmakelint issues

Issues:

./src/icons/CMakeLists.txt:1: Mismatching spaces inside () after command [whitespace/mismatch]
Total Errors: 1
./src/CMakeLists.txt:14: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:88: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:97: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:103: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:111: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:127: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:157: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:163: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:171: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:178: Weird indentation; use 2 spaces [whitespace/indent]
./src/CMakeLists.txt:184: Weird indentation; use 2 spaces [whitespace/indent]
Total Errors: 11
./autotests/CMakeLists.txt:18: Weird indentation; use 2 spaces [whitespace/indent]
Total Errors: 1
./CMakeLists.txt:96: Weird indentation; use 2 spaces [whitespace/indent]
Total Errors: 1