use a regular sokol-shdc compiler glsl shader in the triangle example

build.zig

@@ -429,6 +429,7 @@ fn buildShaders(b: *Build, target: Build.ResolvedTarget) void {
         "texcube.glsl",
         "blend.glsl",
         "vertexpull.glsl",
+        "triangle.glsl",
     };
     const optional_shdc: ?[:0]const u8 = comptime switch (builtin.os.tag) {
         .windows => "win32/sokol-shdc.exe",

src/examples/shaders/triangle.glsl

@@ -0,0 +1,22 @@
+@vs vs
+in vec4 position;
+in vec4 color0;
+
+out vec4 color;
+
+void main() {
+    gl_Position = position;
+    color = color0;
+}
+@end
+
+@fs fs
+in vec4 color;
+out vec4 frag_color;
+
+void main() {
+    frag_color = color;
+}
+@end
+
+@program triangle vs fs