Add includer to gtest for include file tests.

Turn on debug info flag for non-semantic debug test.

gtests/TestFixture.h

@@ -35,6 +35,7 @@
 #ifndef GLSLANG_GTESTS_TEST_FIXTURE_H
 #define GLSLANG_GTESTS_TEST_FIXTURE_H
 
+#include <algorithm>
 #include <cstdint>
 #include <fstream>
 #include <sstream>
@@ -199,9 +200,42 @@ public:
         } else
             shader->setStringsWithLengths(&shaderStrings, &shaderLengths, 1);
         if (!entryPointName.empty()) shader->setEntryPoint(entryPointName.c_str());
-        return shader->parse(
-                (resources ? resources : GetDefaultResources()),
-                defaultVersion, isForwardCompatible, controls);
+
+        // A includer that always assumes header name is a relative path to the test folder.
+        class GlslangTestIncluder : public glslang::TShader::Includer {
+        public:
+            virtual IncludeResult* includeLocal(const char* headerName, const char* /*includerName*/,
+                                                size_t /*inclusionDepth*/) override
+            {
+                std::string path = GLSLANG_TEST_DIRECTORY;
+                path += '/';
+                path += headerName;
+                std::replace(path.begin(), path.end(), '\\', '/');
+
+                auto [success, fileContent] = ReadFile(path);
+                if (success) {
+                    auto buffer = new char[fileContent.size() + 1];
+                    std::copy(fileContent.begin(), fileContent.end(), buffer);
+                    buffer[fileContent.size()] = '\0';
+
+                    return new IncludeResult(headerName, buffer, fileContent.size(), buffer);
+                }
+
+                return nullptr;
+            }
+
+            virtual void releaseInclude(IncludeResult* result) override
+            {
+                if (result != nullptr) {
+                    delete[] static_cast<char*>(result->userData);
+                    delete result;
+                }
+            }
+        };
+
+        GlslangTestIncluder includer;
+        return shader->parse((resources ? resources : GetDefaultResources()), defaultVersion, isForwardCompatible,
+                             controls, includer);
     }
 
     // Compiles and links the given source |code| of the given shader