Meta: Add gn build rules for LibGL and its dependencies

Meta/gn/secondary/Userland/Libraries/LibSoftGPU/BUILD.gn

@@ -0,0 +1,21 @@
+shared_library("LibSoftGPU") {
+  output_name = "softgpu"
+  include_dirs = [ "//Userland/Libraries" ]
+  cflags_cc = [ "-Wno-psabi" ]
+  sources = [
+    "Clipper.cpp",
+    "Device.cpp",
+    "Image.cpp",
+    "PixelConverter.cpp",
+    "Sampler.cpp",
+    "Shader.cpp",
+    "ShaderCompiler.cpp",
+    "ShaderProcessor.cpp",
+  ]
+  deps = [
+    "//AK",
+    "//Userland/Libraries/LibCore",
+    "//Userland/Libraries/LibGPU",
+    "//Userland/Libraries/LibGfx",
+  ]
+}