Compile shaders in build.zig

assets/shaders/gui_text.vert

@@ -8,3 +8,7 @@ layout(location = 1) in vec4 texCoordEM_band_flags;
 layout(location = 2) in vec4 jacobian;
 layout(location = 3) in vec4 scale_offset;
 layout(location = 4) in vec4 color;
+
+void main() {
+    gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
+}