util: improve compiler guard

Glibc 2.26 has dropped xlocale.h, but the functions needed (strtod_l()
and strdof_l()) can be found in stdlib.h.
Improve the detection method to allow newer builds to still make use of
the locale-setting.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102454
Cc: Laurent Carlier <lordheavym@gmail.com>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Laurent Carlier <lordheavym@gmail.com>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>

scons/gallium.py

@@ -157,6 +157,19 @@ def check_header(env, header):
     env = conf.Finish()
     return have_header
 
+def check_functions(env, functions):
+    '''Check if all of the functions exist'''
+
+    conf = SCons.Script.Configure(env)
+    have_functions = True
+
+    for function in functions:
+        if not conf.CheckFunc(function):
+            have_functions = False
+
+    env = conf.Finish()
+    return have_functions
+
 def check_prog(env, prog):
     """Check whether this program exists."""
 
@@ -339,6 +352,9 @@ def generate(env):
         if check_header(env, 'xlocale.h'):
             cppdefines += ['HAVE_XLOCALE_H']
 
+        if check_functions(env, ['strtod_l', 'strtof_l']):
+            cppdefines += ['HAVE_STRTOD_L']
+
     if platform == 'windows':
         cppdefines += [
             'WIN32',