waf: allow to disable libiio at configuration

We default to autodetection for libiio so if the libraries are available
we enable it. However this may not always be desired.

Tools/ardupilotwaf/cxx_checks.py

@@ -162,6 +162,10 @@ def check_lttng(cfg, env):
 
 @conf
 def check_libiio(cfg, env):
+    if cfg.options.disable_libiio:
+        cfg.msg("Checking for 'libiio':", 'disabled', color='YELLOW')
+        return False
+
     cfg.check_cfg(package='libiio', mandatory=False, global_define=True,
                   args=['--libs', '--cflags'])
     env.LIB += cfg.env['LIB_LIBIIO']

wscript

@@ -86,6 +86,10 @@ revisions.
         default=False,
         help="Don't use lttng even if supported by board and dependencies available")
 
+    g.add_option('--disable-libiio', action='store_true',
+        default=False,
+        help="Don't use libiio even if supported by board and dependencies available")
+
 def _collect_autoconfig_files(cfg):
     for m in sys.modules.values():
         paths = []