Expand the cxxstring ABIs, and exclude powerpc64le for now

XGBoost/build_tarballs.jl

@@ -55,10 +55,11 @@ fi
 
 # These are the platforms we will build for by default, unless further
 # platforms are passed in on the command line
-platforms = supported_platforms()
+platforms = expand_cxxstring_abis(supported_platforms())
 
 # Disable FreeBSD for now, because freebsd doesn't have backtrace()
 platforms = [p for p in platforms if !(typeof(p) <: FreeBSD)]
+platforms = [p for p in platforms if !(arch(p) == :powerpc64le)]
 
 # The products that we will ensure are always built
 products = [