Oracle no longer provides the means for our Solaris packagers to make any builds, so we are no longer able to provide binaries for Solaris.
You should still be able to build the product from source. However, you should be aware that there are no continuous build testing done on the combination of Solaris and SPARC anymore (see https://buildfarm.postgresql.org/). There are builds for linux on sparc, but not solaris, as part of the testing (and solaris+sparc for older versions only).
