util: add a function to set umask to 077

Useful to ensure files are written without group/other read rights.

src/common/util.cpp

@@ -413,4 +413,13 @@ std::string get_nix_version_display_string()
     }
     return false;
   }
+  void set_strict_default_file_permissions(bool strict)
+  {
+#if defined(__MINGW32__) || defined(__MINGW__)
+    // no clue about the odd one out
+#else
+    mode_t mode = strict ? 077 : 0;
+    umask(mode);
+#endif
+  }
 }

src/common/util.h

@@ -158,4 +158,6 @@ namespace tools
     /*! \brief where the installed handler is stored */
     static std::function<void(int)> m_handler;
   };
+
+  void set_strict_default_file_permissions(bool strict);
 }