waf: added --save-temps configure option

linking fails with this option, but the ii files are produced, which
is what is needed for diagnosing cache issues

Tools/ardupilotwaf/boards.py

@@ -894,6 +894,9 @@ class chibios(Board):
             cfg.msg("Enabling ChibiOS asserts", "no")
 
 
+        if cfg.env.SAVE_TEMPS:
+            env.CXXFLAGS += [ '-S', '-save-temps=obj' ]
+
         if cfg.options.disable_watchdog:
             cfg.msg("Disabling Watchdog", "yes")
             env.CFLAGS += [ '-DDISABLE_WATCHDOG' ]

wscript

@@ -155,6 +155,11 @@ def options(opt):
         default=False,
         help='enable OS level asserts.')
 
+    g.add_option('--save-temps',
+        action='store_true',
+        default=False,
+        help='save compiler temporary files.')
+    
     g.add_option('--enable-malloc-guard',
         action='store_true',
         default=False,
@@ -387,6 +392,7 @@ def configure(cfg):
     cfg.env.BOOTLOADER = cfg.options.bootloader
     cfg.env.ENABLE_MALLOC_GUARD = cfg.options.enable_malloc_guard
     cfg.env.ENABLE_STATS = cfg.options.enable_stats
+    cfg.env.SAVE_TEMPS = cfg.options.save_temps
 
     cfg.env.HWDEF_EXTRA = cfg.options.extra_hwdef
     if cfg.env.HWDEF_EXTRA: