Correctly reflect declared buffer size for out of order members.

Need to deduce size based on member with highest offset, not highest
index.

reference/shaders-reflection/comp/out-of-order-block-offsets.comp.json

@@ -0,0 +1,44 @@
+{
+    "entryPoints" : [
+        {
+            "name" : "main",
+            "mode" : "comp",
+            "workgroup_size" : [
+                1,
+                1,
+                1
+            ],
+            "workgroup_size_is_spec_constant_id" : [
+                false,
+                false,
+                false
+            ]
+        }
+    ],
+    "types" : {
+        "_7" : {
+            "name" : "SSBO",
+            "members" : [
+                {
+                    "name" : "foo",
+                    "type" : "uint",
+                    "offset" : 8
+                },
+                {
+                    "name" : "bar",
+                    "type" : "uint",
+                    "offset" : 4
+                }
+            ]
+        }
+    },
+    "ssbos" : [
+        {
+            "type" : "_7",
+            "name" : "SSBO",
+            "block_size" : 12,
+            "set" : 0,
+            "binding" : 0
+        }
+    ]
+}

shaders-reflection/comp/out-of-order-block-offsets.comp

@@ -0,0 +1,12 @@
+#version 450
+
+layout(set = 0, binding = 0) buffer SSBO
+{
+	layout(offset = 8) uint foo;
+	layout(offset = 4) uint bar;
+};
+
+void main()
+{
+	bar = foo;
+}

spirv_cross.cpp

@@ -1729,10 +1729,22 @@ size_t Compiler::get_declared_struct_size(const SPIRType &type) const
 	if (type.member_types.empty())
 		SPIRV_CROSS_THROW("Declared struct in block cannot be empty.");
 
-	uint32_t last = uint32_t(type.member_types.size() - 1);
-	size_t offset = type_struct_member_offset(type, last);
-	size_t size = get_declared_struct_member_size(type, last);
-	return offset + size;
+	// Offsets can be declared out of order, so we need to deduce the actual size
+	// based on last member instead.
+	uint32_t member_index = 0;
+	size_t highest_offset = 0;
+	for (uint32_t i = 0; i < uint32_t(type.member_types.size()); i++)
+	{
+		size_t offset = type_struct_member_offset(type, i);
+		if (offset > highest_offset)
+		{
+			highest_offset = offset;
+			member_index = i;
+		}
+	}
+
+	size_t size = get_declared_struct_member_size(type, member_index);
+	return highest_offset + size;
 }
 
 size_t Compiler::get_declared_struct_size_runtime_array(const SPIRType &type, size_t array_size) const