package: adapt GLTests Jenkins configuration to previous change.
package: add Git configuration also to GLTests Jenkins configuration.

So we have nice changelogs from build to build. We now need to run the
tests sequentially, because the building instances would try to access
the git repository all at once.
package: Fail GLTests Jenkins job if the build fails.
package: set RPATH to install dir so the proper dependencies are used.
external: install gl2ext.h also for ES3.

Again, didn't bother with testing.
Shaders: fix tests in static build.