[DTLTO][Clang][Docs] Update for COFF support (llvm#149988)

As the COFF linker is usually invoked independently, update the Clang
DTLTO section to show an example. This follows what is done earlier in
the document.

Also some minor fixes and improvements:
- Use generic distributor names to avoid implying anything about what an
Incredibuild distributor may or should support.
- Use subheadings for readability.
- Correct a mis-cased hyperlink.

Author: bd1976bris

clang/docs/ThinLTO.rst

@@ -249,6 +249,9 @@ during the traditional link step.
 
 The implementation is documented here: https://llvm.org/docs/DTLTO.html.
 
+Command-Line Options
+^^^^^^^^^^^^^^^^^^^^
+
 DTLTO requires the LLD linker (``-fuse-ld=lld``).
 
 ``-fthinlto-distributor=<path>``
@@ -260,17 +263,29 @@ DTLTO requires the LLD linker (``-fuse-ld=lld``).
    - Can be specified multiple times to pass multiple options.
    - Multiple options can also be specified by separating them with commas.
 
-Examples:
-   - ``clang -flto=thin -fthinlto-distributor=incredibuild.exe -Xthinlto-distributor=--verbose,--j10 -fuse-ld=lld``
-   - ``clang -flto=thin -fthinlto-distributor=$(which python) -Xthinlto-distributor=incredibuild.py -fuse-ld=lld``
-
 If ``-fthinlto-distributor=`` is specified, Clang supplies the path to a
 compiler to be executed remotely to perform the ThinLTO backend
 compilations. Currently, this is Clang itself.
 
+Usage
+^^^^^
+
+Compilation is unchanged from ThinLTO. DTLTO options need to supplied for the link step:
+
+.. code-block:: console
+
+  % clang -flto=thin -fthinlto-distributor=distribute.sh -Xthinlto-distributor=--verbose,--j10 -fuse-ld=lld file1.o file2.o
+  % clang -flto=thin -fthinlto-distributor=$(which python) -Xthinlto-distributor=distribute.py -fuse-ld=lld file1.o file2.o
+
+When using lld-link:
+
+.. code-block:: console
+
+  % lld-link /out:a.exe file1.obj file2.obj /thinlto-distributor:distribute.exe /thinlto-remote-compiler:${LLVM}\bin\clang.exe /thinlto-distributor-arg:--verbose
+
 Note that currently, DTLTO is only supported in some LLD flavors. Support can
 be added to other LLD flavours in the future.
-See `DTLTO <https://lld.llvm.org/dtlto.html>`_ for more information.
+See `DTLTO <https://lld.llvm.org/DTLTO.html>`_ for more information.
 
 More Information
 ================