progs/trivial: add fflushes for cygwin
diff --git a/progs/trivial/tri-cull-both.c b/progs/trivial/tri-cull-both.c
index 73c5583..864be71 100644
--- a/progs/trivial/tri-cull-both.c
+++ b/progs/trivial/tri-cull-both.c
@@ -39,6 +39,7 @@
    fprintf(stderr, "GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
    fprintf(stderr, "GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
    fprintf(stderr, "GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
+   fflush(stderr);
 
    glClearColor(0.0, 0.0, 1.0, 0.0);
    glCullFace(GL_FRONT_AND_BACK);