egl: fix entrypoint sorting test

Fixes: 68dc591af1 "egl: Fix eglentrypoint.h sort order."
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Tapani Pälli <tapani.palli@intel.com>
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Mathias Fröhlich <Mathias.Froehlich@web.de>

src/egl/egl-entrypoint-check

@@ -7,5 +7,5 @@ then
 fi
 
 entrypoints=$(grep EGL_ENTRYPOINT "$srcdir"/main/eglentrypoint.h)
-sorted=$(sort <<< "$entrypoints")
+sorted=$(LANG=C sort <<< "$entrypoints")
 test "$entrypoints" = "$sorted"