It's your 4th hypothesis, "C compiler".
This is confirmed by the file you linked, which states at the top:
This file contains the module types for compiling C/C++ for Android, and converts the properties into the flags and filenames necessary to pass to the compiler.
And the StackOverflow tag also states:
cc is a common name for a C compiler executable or driver.
Furthermore, the file you linked is very clearly used for compiling C / C++, with hundreds if not thousands of references to the process.
I'm not 100% sure what you're after, since you seem to have managed to find the answer yourself!