Change to Oracle Developer Studio 12.6 for building on Solaris at Oracle

It's time for Oracle to change the official compiler used for building OpenJDK on Solaris. The new version will be Oracle Developer Studio 12.6 and the build will happen on Solaris 11.3.

The required minimum package versions are:
developer/developerstudio-126/backend 12.6-1.0.0.1
developer/developerstudio-126/c++ 12.6-1.0.2.0
developer/developerstudio-126/cc 12.6-1.0.1.0
developer/developerstudio-126/dbx 12.6-1.0.0.1
developer/developerstudio-126/library/c++-libs 12.6-1.0.2.0
developer/developerstudio-126/library/c-libs 12.6-1.0.0.1
developer/developerstudio-126/library/f90-libs 12.6-1.0.0.1
developer/developerstudio-126/library/math-libs 12.6-1.0.0.1
developer/developerstudio-126/library/studio-gccrt 12.6-1.0.0.1
developer/developerstudio-126/studio-common 12.6-1.0.0.1
developer/developerstudio-126/studio-ja 12.6-1.0.0.1
developer/developerstudio-126/studio-legal 12.6-1.0.0.1
developer/developerstudio-126/studio-zhCN 12.6-1.0.0.1