sal: avoid STL asserts in create_merged_environment

"Assertion failed: sequence not ordered" printed when running smoketest

Change-Id: Id9b7541f43342adf62137718dc332c0187c32f57

sal/osl/w32/procimpl.cxx

@@ -129,6 +129,11 @@ namespace /* private */
             p += l + 1;
         }
         FreeEnvironmentStrings(env);
+
+        // it is apparently possible that the environment is not completely
+        // sorted; Cygwin may append entries, which breaks the equal_range
+        std::stable_sort(environment->begin(), environment->end(),
+            less_environment_variable());
     }
 
     /* the environment list must be sorted, new values