progs: Get more samples building on windows.

progs/util/SConscript

@@ -0,0 +1,15 @@
+Import('env')
+
+env = env.Clone()
+
+util = env.StaticLibrary(
+    target = ['util'],
+    source = [
+        'readtex.c',
+        'trackball.c',
+        'showbuffer.c',
+        'shaderutil.c',
+    ],
+)
+
+Export('util')