use conf.env['SAMPLERATE'] to determine wether samplerate is available instead of conf.is_defined('HAVE_SAMPLERATE')

common/wscript

@@ -6,8 +6,8 @@ import re
 import os
 
 def configure(conf):
-    conf.env['BUILD_NETLIB'] = conf.is_defined('HAVE_SAMPLERATE')
-    conf.env['BUILD_ADAPTER'] = conf.is_defined('HAVE_SAMPLERATE')
+    conf.env['BUILD_NETLIB'] = conf.env['SAMPLERATE']
+    conf.env['BUILD_ADAPTER'] = conf.env['SAMPLERATE']
 
     if conf.env['IS_WINDOWS']:
         try:

example-clients/wscript

@@ -51,7 +51,7 @@ def configure(conf):
 
     conf.env['BUILD_EXAMPLE_CLIENT_REC'] = conf.is_defined('HAVE_SNDFILE')
 
-    conf.env['BUILD_EXAMPLE_ALSA_IO'] = conf.is_defined('HAVE_SAMPLERATE') and conf.env['BUILD_DRIVER_ALSA']
+    conf.env['BUILD_EXAMPLE_ALSA_IO'] = conf.env['SAMPLERATE'] and conf.env['BUILD_DRIVER_ALSA']
 
 def build(bld):
     if bld.env['IS_LINUX']:

wscript

@@ -495,6 +495,9 @@ def configure(conf):
 
     if conf.is_defined('HAVE_SAMPLERATE'):
         conf.env['LIB_SAMPLERATE'] = ['samplerate']
+        conf.env['SAMPLERATE'] = True
+    else:
+        conf.env['SAMPLERATE'] = False
 
     conf.sub_config('common')
     if conf.env['IS_LINUX']: