docs: correct flags for 5.3+ installed image

The `-sdk` handling requires `-resource-dir` for nows.

Author: compnerd

README.md

@@ -17,7 +17,7 @@ This requires the 5.3 or newer. You can use the the release binaries from [swift
 The following example session shows how to build with CMake 3.16 or newer.
 
 ```cmd
-set SWIFTFLAGS=-sdk %SDKROOT% -I %SDKROOT%/usr/lib/swift -L %SDKROOT%/usr/lib/swift/windows
+set SWIFTFLAGS=-sdk %SDKROOT% -resource-dir %SDKROOT%/usr/lib/swift -I %SDKROOT%/usr/lib/swift -L %SDKROOT%/usr/lib/swift/windows
 
 cmake -B build -D BUILD_SHARED_LIBS=YES -D CMAKE_BUILD_TYPE=Release -D CMAKE_Swift_FLAGS="%SWIFTFLAGS%" -G Ninja -S .
 ninja -C build SwiftWin32 UICatalog