add git hash in generated source file

[t-bltg]

Add the wrapit tool git hash in the generated source files, for reproducibility.

[grasph]

@t-bltg please review the changes I made to your PR.

[t-bltg]

Hum, the file version.cmake seems to be missing in https://github.com/grasph/wrapit/pull/25/commits/e8e9ca9ef8c8eb4d65cd0ebf9528b908616a03fe, so it fails to build.

[t-bltg]

I've used target_sources instead, since you cannot use a missing source in add_executable (version.cpp), which would be created by the version target (fails to build).

[grasph]

The error was still there with your fix. I don't how I missed it before. It works for me with the trick of 6785d2d commit.

[t-bltg]

Odd, this worked on my laptop, and I extra checked by removing CMAKE_BINARY_DIR before invoking cmake.

Anyway, I can confirm that it now builds as expected.

[t-bltg]

Thanks !