build: build SwiftSyntax before the toolchain build

Perform a build of Swift Syntax prior to the build of the toolchain so
that we can enable the early swift syntax parser builds.  This is a
prerequisite for enabling macros on Windows.

Author: compnerd

utils/build-windows-toolchain.bat

@@ -188,6 +188,30 @@ cmake ^
 cmake --build "%BuildRoot%\curl" || (exit /b)
 cmake --build "%BuildRoot%\curl" --target install || (exit /b)
 
+:: Build Swift Syntax
+cmake ^
+  -B "%BuildRoot%\99" ^
+
+  -D CMAKE_BUILD_TYPE=%CMAKE_BUILD_TYPE% ^
+  -D CMAKE_C_COMPILER=%BuildRoot%/1/bin/clang-cl.exe ^
+  -D CMAKE_C_FLAGS="/GS- /Oy /Gw /Gy" ^
+  -D CMAKE_CXX_COMPILER=cl ^
+  -D CMAKE_CXX_FLAGS="/GS- /Oy /Gw /Gy" ^
+  -D CMAKE_MT=mt ^
+  -D CMAKE_Swift_COMPILER=%BuildRoot%/toolchains/PFiles64/Swift/Toolchains/0.0.0+Asserts/usr/bin/swiftc.exe ^
+  -D CMAKE_Swift_FLAGS="-sdk %BuildRoot%/toolchains/PFiles64/Swift/Platforms/Windows.platform/Developer/SDKs/Windows.sdk" ^
+  -D CMAKE_EXE_LINKER_FLAGS="/INCREMENTAL:NO" ^
+  -D CMAKE_SHARED_LINKER_FLAGS="/INCREMENTAL:NO" ^
+
+  -D CMAKE_INSTALL_PREFIX="%InstallRoot%" ^
+
+  -D SWIFT_SYNTAX_ENABLE_WMO_PRE_3_26=YES ^
+
+  -G Ninja ^
+  -S %SourceRoot%\swift-syntax || (exit /b)
+cmake --build %BuildRoot%\99 || (exit /b)
+cmake --build %BuildRoot%\99 --target install || (exit /b)
+
 :: Build Toolchain
 cmake ^
   -B "%BuildRoot%\1" ^