`dxr.exe` doesn't support macro definitions via its CLI

Description
It would be extremely useful if the Rewriter (dxr.exe) supported the -D command-line parameter similar to dxc.exe. After all, it's similar to the preprocessor.

In the absence of this functionality, I had to generate source files with #ifdefs in order to rewrite the same source with different macros.

What's worse, dxr.exe accepts -D arguments without errors or warnings and rewrites the source ignoring the macros, which may take some experimentation to realize.

Steps to Reproduce

• Compile this trivial shader with -D float4=0: https://godbolt.org/z/5q5WKvq6e The compilation fails, which proves that the macro was expanded.
• Now, rewrite the same shader with dxr.exe -D float4=0 -E PSMain. The file is rewritten verbatim, which proves that the macro wasn't expanded.

Environment

• DXC version: 1.7.2212
• Host Operating System: Win 10

Start at the dxr.exe command-line handling and compare how dxc.exe processes -D arguments. Reproduce the shader example with and without -D float4=0 and inspect the rewrite path for PSMain. Done means dxr.exe applies macro definitions during rewriting and no longer silently ignores them.