Enable preprocessor optimization of ESSL 1.0

Since #7358 is blocked by an upstream spirv-cross issue, we can at least do a
bit of preprocessor optimization for ESSL 1.0 code in the meantime and introduce
the FILAMENT_EFFECTIVE_VERSION preprocessor definitions.

libs/filamat/src/GLSLPostProcessor.cpp

@@ -23,6 +23,7 @@
 #include <spirv_glsl.hpp>
 #include <spirv_msl.hpp>
 
+#include "backend/DriverEnums.h"
 #include "sca/builtinResource.h"
 #include "sca/GLSLTools.h"
 
@@ -395,7 +396,11 @@ bool GLSLPostProcessor::process(const std::string& inputShader, Config const& co
             break;
         case MaterialBuilder::Optimization::SIZE:
         case MaterialBuilder::Optimization::PERFORMANCE:
-            fullOptimization(tShader, config, internalConfig);
+            if (config.featureLevel == filament::backend::FeatureLevel::FEATURE_LEVEL_0) {
+                preprocessOptimization(tShader, config, internalConfig);
+            } else {
+                fullOptimization(tShader, config, internalConfig);
+            }
             break;
     }