progs/trivial: add fflushes for cygwin
diff --git a/progs/trivial/readpixels.c b/progs/trivial/readpixels.c
index 88aac26..5671618 100644
--- a/progs/trivial/readpixels.c
+++ b/progs/trivial/readpixels.c
@@ -17,6 +17,7 @@
    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(0.3, 0.1, 0.3, 0.0);
 }