Only import msvccompiler on win32 platforms.

Lib/distutils/command/build_ext.py

@@ -624,9 +624,9 @@ class build_ext (Command):
         # pyconfig.h that MSVC groks.  The other Windows compilers all seem
         # to need it mentioned explicitly, though, so that's what we do.
         # Append '_d' to the python import library on debug builds.
+        if sys.platform == "win32":
             from distutils.msvccompiler import MSVCCompiler
-        if sys.platform == "win32" and \
-           not isinstance(self.compiler, MSVCCompiler):
+            if not isinstance(self.compiler, MSVCCompiler):
                 template = "python%d%d"
                 if self.debug:
                     template = template + '_d'