Tell CMake to not check for a C++ compiler

[aperezdc]

By default CMake checks both for C and C++ compilers, while the latter is not needed. Setting the list of languages to just C in the call to project() removes the unneeded check.

[aperezdc]

JFTR, I found out that the unneeded C++ check was being done thanks to this report from Buildroot's autobuilder 🔧

[fred-wang]

Thanks, this LGTM. @eustas can you please review this?

Cmake reference: https://cmake.org/cmake/help/v3.11/command/project.html

[eustas]

I believe CMake 2.8.6 do not recognize LANGUAGES keyword. We can omit it, because there is no VERSION part.

[aperezdc]

@eustas If you need to support CMake 2.8, according to the documentation it is possible to use:

project(brotli C)

I'll check whether omitting the LANGUAGES keyword works also in more recent versions (my local version is 3.10.x) and update the PR.

[aperezdc]

The plain project(brotli C) worked fine for me with CMake 3.10.3, so I have updated the PR. Hopefully the CI will pass as well 😉

[eustas]

Thanks!