[docs] add Windows examples to ThinLTO.rst

[ruiu]

LGTM

clang/docs/ThinLTO.rst

 
 - **gold (via the gold-plugin)**:
   Similar to monolithic LTO, this requires using
   a `gold linker configured with plugins enabled
   <http://llvm.org/docs/GoldPlugin.html>`_.
 - **ld64**:
   Starting with `Xcode 8 <https://developer.apple.com/xcode/>`_.
 - **lld**:
-  Starting with r284050 (ELF only).
+  Starting with r284050 for ELF, r298942 for COFF.
 
 Usage
 =====
 
 Basic
 -----
 
 To utilize ThinLTO, simply add the -flto=thin option to compile and link. E.g.
 
 .. code-block:: console
 
   % clang -flto=thin -O2 file1.c file2.c -c
   % clang -flto=thin -O2 file1.o file2.o -o a.out
 
+When using lld-link, the -flto option need only be added to the compile step:
+
+.. code-block:: console
+
+  % clang-cl -flto=thin -O2 -c file1.c file2.c
+  % lld-link /out:a.exe file1.obj file2.obj
+
 As mentioned earlier, by default the linkers will launch the ThinLTO backend
 threads in parallel, passing the resulting native object files back to the
 linker for the final native link.  As such, the usage model the same as
 non-LTO.
 
 With gold, if you see an error during the link of the form:
 
 .. code-block:: console

 be reduced to ``N`` via:
 
 - gold:
   ``-Wl,-plugin-opt,jobs=N``
 - ld64:
   ``-Wl,-mllvm,-threads=N``
 - lld:
   ``-Wl,--thinlto-jobs=N``
+- lld-link:
+  ``/opt:lldltojobs=N``
 
 Incremental
 -----------
 .. _incremental:
 
 ThinLTO supports fast incremental builds through the use of a cache,
 which currently must be enabled through a linker option.
 
 - gold (as of LLVM 4.0):
   ``-Wl,-plugin-opt,cache-dir=/path/to/cache``
 - ld64 (support in clang 3.9 and Xcode 8):
   ``-Wl,-cache_path_lto,/path/to/cache``
 - ELF lld (as of LLVM 5.0):
   ``-Wl,--thinlto-cache-dir=/path/to/cache``
-- COFF lld (as of LLVM 6.0):
+- COFF lld-link (as of LLVM 6.0):
   ``/lldltocache:/path/to/cache``
 
 Cache Pruning
 -------------
 
 To help keep the size of the cache under control, ThinLTO supports cache
 pruning. Cache pruning is supported with ld64 and ELF and COFF lld, but
 currently only ELF and COFF lld allow you to control the policy with a
 policy string. The cache policy must be specified with a linker option.
 
 - ELF lld (as of LLVM 5.0):
   ``-Wl,--thinlto-cache-policy,POLICY``
-- COFF lld (as of LLVM 6.0):
+- COFF lld-link (as of LLVM 6.0):
   ``/lldltocachepolicy:POLICY``
 
 A policy string is a series of key-value pairs separated by ``:`` characters.
 Possible key-value pairs are:
 
 - ``cache_size=X%``: The maximum size for the cache directory is ``X`` percent
   of the available space on the the disk. Set to 100 to indicate no limit,
   50 to indicate that the cache size will not be left over half the available

 1. The host compiler_ must be a version of clang that supports ThinLTO.
 #. The host linker_ must support ThinLTO (and in the case of gold, must be
    `configured with plugins enabled <http://llvm.org/docs/GoldPlugin.html>`_.
 #. Use the following additional `CMake variables
    <http://llvm.org/docs/CMake.html#options-and-variables>`_
    when configuring the bootstrap compiler build:
 
   * ``-DLLVM_ENABLE_LTO=Thin``
-  * ``-DLLVM_PARALLEL_LINK_JOBS=1``
-    (since the ThinLTO link invokes parallel backend jobs)
   * ``-DCMAKE_C_COMPILER=/path/to/host/clang``
   * ``-DCMAKE_CXX_COMPILER=/path/to/host/clang++``
   * ``-DCMAKE_RANLIB=/path/to/host/llvm-ranlib``
   * ``-DCMAKE_AR=/path/to/host/llvm-ar``
 
+  Or, on Windows:
+
+  * ``-DLLVM_ENABLE_LTO=Thin``
+  * ``-DCMAKE_C_COMPILER=/path/to/host/clang-cl.exe``
+  * ``-DCMAKE_CXX_COMPILER=/path/to/host/clang-cl.exe``
+  * ``-DCMAKE_LINKER=/path/to/host/lld-link.exe``
+  * ``-DCMAKE_RANLIB=/path/to/host/llvm-ranlib.exe``
+  * ``-DCMAKE_AR=/path/to/host/llvm-ar.exe``
+
 #. To use additional linker arguments for controlling the backend
    parallelism_ or enabling incremental_ builds of the bootstrap compiler,
    after configuring the build, modify the resulting CMakeCache.txt file in the
    build directory. Specify any additional linker options after
    ``CMAKE_EXE_LINKER_FLAGS:STRING=``. Note the configure may fail if
    linker plugin options are instead specified directly in the previous step.
 
 More Information
 ================
 
 * From LLVM project blog:
   `ThinLTO: Scalable and Incremental LTO
   <http://blog.llvm.org/2016/06/thinlto-scalable-and-incremental-lto.html>`_