Import dso_suffix from spack.build_environment in abi.py (#2174)

Fixes #1845

lib/spack/spack/abi.py

@@ -26,6 +26,7 @@
 import os
 import spack
 import spack.spec
+from spack.build_environment import dso_suffix
 from spack.spec import CompilerSpec
 from spack.util.executable import Executable, ProcessError
 from llnl.util.lang import memoized