gpu/internal/shaders: generate shader variants

We're about to add Direct3D support, where shaders are written in
HLSL. Rather than write shaders twice (or more), convert them to
a GLSL variant understood by the glslcc cross-compiler and generate
the OpenGL ES 2.0 and HLSL variants. The HLSL is used by a future
change.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/gen.go

@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package gpu
+
+//go:generate go run build.go