A 64-bit build results in a segfault in the parsers module (on both SPARC
and x86).  Dialing down the optimization to -xO1 eliminates the crash.

In order to only lower the optimization for the one object that needs it
and only in a 64-bit build, we do some monkeypatching of the distutils
compiler class, and replace its _compile() method with one that does that
check and replaces the original optimization level with the lower one.

This patch can be removed when we move to Studio 12.5.

--- a/setup.py	2017-02-01 08:18:58.000000000 -0800
+++ b/setup.py	2017-02-03 18:13:20.479471297 -0800
@@ -302,7 +302,18 @@
 
         return build_ext.build_extensions(self)
 
+    def my_compile(self, obj, src, ext, cc_args, extra_postargs, pp_opts):
+        if src == "mercurial/parsers.c" and "-m64" in self.compiler.compiler_so:
+            for i, arg in enumerate(self.compiler.compiler_so):
+                if arg.startswith("-xO"):
+                    break
+            self.compiler.compiler_so[i] = "-xO1"
+        self.compiler.old_compile(obj, src, ext, cc_args, extra_postargs, pp_opts)
+
     def build_extension(self, ext):
+        if not hasattr(self.compiler, "old_compile"):
+            self.compiler.old_compile = self.compiler._compile
+            self.compiler._compile = self.my_compile
         try:
             build_ext.build_extension(self, ext)
         except CCompilerError: