Selectable renderer implementation (#1247)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/mbgl/gl/renderer_backend.cpp

@@ -4,9 +4,12 @@
 #include <mbgl/gl/context.hpp>
 #include <mbgl/gl/extension.hpp>
 #include <mbgl/shaders/shader_manifest.hpp>
-#include <mbgl/shaders/gl/shader_group_gl.hpp>
 #include <mbgl/util/logging.hpp>
 
+#if MLN_DRAWABLE_RENDERER
+#include <mbgl/shaders/gl/shader_group_gl.hpp>
+#endif
+
 #include <cassert>
 
 namespace mbgl {
@@ -66,6 +69,7 @@ void RendererBackend::setScissorTest(bool enabled) {
 
 RendererBackend::~RendererBackend() = default;
 
+#if MLN_DRAWABLE_RENDERER
 /// @brief Register a list of types with a shader registry instance
 /// @tparam ...ShaderID Pack of BuiltIn:: shader IDs
 /// @param registry A shader registry instance
@@ -98,6 +102,7 @@ void RendererBackend::initShaders(gfx::ShaderRegistry& shaders, const ProgramPar
                   shaders::BuiltIn::FillPatternShader,
                   shaders::BuiltIn::RasterShader>(shaders, programParameters);
 }
+#endif
 
 } // namespace gl
 } // namespace mbgl