Thanks for your detailed answer.
If I wanted to pass multiple arguments with the -D option in the command line, how would I do that? I thought I just had to sperate them with a semicolon, but this didn’t work:
cmake -S source -B build -DFREETYPE_INCLUDE_DIR_freetype2:PATH=/usr/include/freetype2;FREETYPE_INCLUDE_DIR_ft2build:PATH=/usr/include/freetype2;FREETYPE_LIBRARY_DEBUG:FILEPATH=FREETYPE_LIBRARY_DEBUG-NOTFOUND;FREETYPE_LIBRARY_RELEASE:FILEPATH=/usr/lib/x86_64-linux-gnu/libfreetype.so