Use backslash-separated source paths in config.w32

confutils' ADD_SOURCES derives each object's directory by splitting on
backslashes only; with forward slashes the objects compiled flat into
the build directory while the link response file expected them under
src\, failing with LNK1181.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013j6ePxd1BobZkr8YVLnNet

Author: ondrejmirtes

turbo-ext/config.w32

@@ -15,12 +15,13 @@ if (PHP_PHPSTAN_TURBO != "no") {
 	// generated parser action files exceed the default section limit.
 	// The version is passed as a bare token (main.cpp stringizes it) —
 	// quote characters do not survive the configure-to-nmake pipeline.
-	// The version is passed as a bare token (main.cpp stringizes it) —
-	// quote characters do not survive the configure-to-nmake pipeline.
 	var flags = "/std:c++17 /EHsc /bigobj /DPHPSTANTURBO_VERSION_RAW=" + version;
 
+	// backslash-separated paths: confutils' ADD_SOURCES derives the object
+	// directory by splitting on backslashes only — with forward slashes the
+	// objects compile flat while the link list expects the subpath
 	EXTENSION("phpstan_turbo",
-		"src/main.cpp src/support.cpp src/CombinationsHelper.cpp src/ConditionalExpressionHolder.cpp src/ExpressionTypeHolder.cpp src/NodeScanner.cpp src/NodeTraverser.cpp src/ScopeOps.cpp src/TrinaryLogic.cpp src/TypeCombinatorCache.cpp",
+		"src\\main.cpp src\\support.cpp src\\CombinationsHelper.cpp src\\ConditionalExpressionHolder.cpp src\\ExpressionTypeHolder.cpp src\\NodeScanner.cpp src\\NodeTraverser.cpp src\\ScopeOps.cpp src\\TrinaryLogic.cpp src\\TypeCombinatorCache.cpp",
 		true,
 		flags);
 	ADD_SOURCES(configure_module_dirname + "/src/parser",