rawtherapee: fix version information

The existing version logic dates to 68a38d6c0f (PR 18368 on
September 25, 2016). But rawtherapee switched from hg to git
around 2015, so these cmake variables were wrong almost as soon
as they were set.

Without this patch, running

    rawtherapee-cli --version

has the output

    RawTherapee, version , command line.

With this patch:

    RawTherapee, version 5.12, command line.

which is significantly better, although personally I'd prefer to also
have a git commit ID.

pkgs/applications/graphics/rawtherapee/default.nix

@@ -50,7 +50,15 @@ stdenv.mkDerivation rec {
   };
 
   postPatch = ''
-    echo "set(HG_VERSION ${version})" > ReleaseInfo.cmake
+    cat <<EOF > ReleaseInfo.cmake
+    set(GIT_DESCRIBE ${version})
+    set(GIT_BRANCH ${version})
+    set(GIT_VERSION ${version})
+    # Missing GIT_COMMIT and GIT_COMMIT_DATE, which are not easy to obtain.
+    set(GIT_COMMITS_SINCE_TAG 0)
+    set(GIT_COMMITS_SINCE_BRANCH 0)
+    set(GIT_VERSION_NUMERIC_BS ${version})
+    EOF
     substituteInPlace tools/osx/Info.plist.in rtgui/config.h.in \
       --replace "/Applications" "${placeholder "out"}/Applications"
   '';