ShaderGen: Don't use __VERSION__ for polyfill

Adreno once again is a broken turd and uses 300 even for GLSL ES 3.20.

And to add insult to injury, it reports the errors at the call site
instead of where the function is actually being overloaded...

src/util/shadergen.cpp

@@ -29,7 +29,10 @@ ShaderGen::ShaderGen(RenderAPI render_api, GPUShaderLanguage shader_language, bo
   {
 #ifdef ENABLE_OPENGL
     if (m_render_api == RenderAPI::OpenGL || m_render_api == RenderAPI::OpenGLES)
-      m_glsl_version_string = GetGLSLVersionString(m_render_api, GetGLSLVersion(render_api));
+    {
+      m_glsl_version = GetGLSLVersion(render_api);
+      m_glsl_version_string = GetGLSLVersionString(m_render_api, m_glsl_version);
+    }
 
     m_use_glsl_interface_blocks =
       (shader_language == GPUShaderLanguage::GLSLVK || GLAD_GL_ES_VERSION_3_2 || GLAD_GL_VERSION_3_2);
@@ -349,11 +352,9 @@ void ShaderGen::WriteHeader(std::stringstream& ss, bool enable_rov /* = false */
   }
 
   // Pack functions missing from GLSL ES 3.0.
-  if (!m_glsl || m_shader_language == GPUShaderLanguage::GLSLES)
+  // We can't rely on __VERSION__ because Adreno is a broken turd and reports 300 even for GLES 3.2.
+  if (!m_glsl || (m_shader_language == GPUShaderLanguage::GLSLES && m_glsl_version < 310))
   {
-    if (m_shader_language == GPUShaderLanguage::GLSLES)
-      ss << "#if __VERSION__ < 310\n";
-
     ss << "uint packUnorm4x8(float4 value) {\n"
           "  uint4 packed = uint4(round(saturate(value) * 255.0));\n"
           "  return packed.x | (packed.y << 8) | (packed.z << 16) | (packed.w << 24);\n"
@@ -363,9 +364,6 @@ void ShaderGen::WriteHeader(std::stringstream& ss, bool enable_rov /* = false */
           "  uint4 packed = uint4(value & 0xffu, (value >> 8) & 0xffu, (value >> 16) & 0xffu, value >> 24);\n"
           "  return float4(packed) / 255.0;\n"
           "}\n";
-
-    if (m_shader_language == GPUShaderLanguage::GLSLES)
-      ss << "#endif\n";
   }
 
   ss << "\n";

src/util/shadergen.h

@@ -76,5 +76,6 @@ protected:
   bool m_use_glsl_binding_layout = false;
   mutable bool m_has_uniform_buffer = false;
 
+  u32 m_glsl_version = 0;
   TinyString m_glsl_version_string;
 };