Scons: check for timespec_get on windows as well as unices

windows has a timespec_get function, and if we don't check that then it
will try to fall back to using clock_gettime, which windows doesn't
have.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8592>

scons/gallium.py

@@ -340,6 +340,10 @@ def generate(env):
         cppdefines += ['NDEBUG']
     if env['build'] == 'profile':
         cppdefines += ['PROFILE']
+
+    if check_functions(env, ['timespec_get']):
+        cppdefines += ['HAVE_TIMESPEC_GET']
+
     if env['platform'] in ('posix', 'linux', 'freebsd', 'darwin'):
         cppdefines += [
             '_POSIX_SOURCE',
@@ -374,9 +378,6 @@ def generate(env):
         if check_functions(env, ['random_r']):
             cppdefines += ['HAVE_RANDOM_R']
 
-        if check_functions(env, ['timespec_get']):
-            cppdefines += ['HAVE_TIMESPEC_GET']
-
         if check_header(env, 'sys/shm.h'):
             cppdefines += ['HAVE_SYS_SHM_H']