test(backend): add GCC include path syntax test for Windows platform

- Add testGccOnWindowsUsesGccIncludeSyntaxForAllSourceTypes method to verify include path formatting
- Test include paths with GCC compiler on Windows for C, C++, and assembler files
- Verify that GCC uses -I flag syntax instead of /I for all source types on Windows
- Confirm proper escaping of include paths with spaces using escapeshellarg
- Add formatIncludePaths method to handle include flag formatting consistently across platforms

phpunit/src/Backend/BackendTest.php

@@ -213,6 +213,27 @@ class BackendTest extends TestCase
         $this->assertStringContainsString('-fno-rtti', $cmd);
     }
 
+    public function testGccOnWindowsUsesGccIncludeSyntaxForAllSourceTypes(): void
+    {
+        $compiler = new Gcc(new Windows());
+        $includePaths = ['C:\\phpx\\include', 'C:\\Program Files\\PHP\\include'];
+        $options = [
+            'include_paths' => $includePaths,
+        ];
+        $commands = [
+            $compiler->buildCompileCommand('test.cpp', 'test.obj', $options),
+            $compiler->buildCCompileCommand('test.c', 'test.obj', $options),
+            $compiler->buildNativeCompileCommand('test.S', 'test.obj', $options, 'assembler'),
+        ];
+
+        foreach ($commands as $cmd) {
+            foreach ($includePaths as $path) {
+                $this->assertStringContainsString('-I' . escapeshellarg($path), $cmd);
+            }
+            $this->assertStringNotContainsString('/I ', $cmd);
+        }
+    }
+
     public function testGccBuildCCompileCommandKeepsSharedCompilerOptions(): void
     {
         $platform = new Linux();

src/Backend/GccLikeBackend.php

@@ -51,6 +51,17 @@ abstract class GccLikeBackend extends CompilerBackend
         return '-o';
     }
 
+    /** Include flag syntax is defined by the compiler driver, not the host platform. */
+    protected function formatIncludePaths(array $includePaths): string
+    {
+        $flags = [];
+        foreach ($includePaths as $path) {
+            $flags[] = '-I' . escapeshellarg($path);
+        }
+
+        return implode(' ', $flags);
+    }
+
     /** Format the sanitizer flag. */
     protected function formatSanitizerFlag(string $sanitizer): string
     {