Update Windows.md

Update the cmake configuration to actually reflect the current state of the world.  This now builds against the MSVC built LLVM/clang and builds with clang-cl.  This also enables building the test suite since that is starting to work on Windows.  The MSVC commands are still out of date, but this is an overall improvement to the instructions.  Since the primary work shifted towards Windows x86_64, we can use the prebuilt binaries for ICU from the ICU project as they provide Windows x86_64 builds.

Author: compnerd

docs/WindowsBuild.md

@@ -10,6 +10,7 @@ There are two supported ways to build Swift on Windows, they are
 1. Using the Microsoft Visual C++ compiler (MSVC)
 
 `clang-cl` is recommended over MSVC for building Swift on Windows.
+
 Although it is possible to build the compiler and the standard library with
 MSVC and to use those built products to compile a Swift program, it won't be
 possible to run the binary without separately obtaining the Swift runtime. On
@@ -39,17 +40,9 @@ it provides some of the needed headers and libraries.
 - Currently, other repositories in the Swift project have not been tested and
   may not be supported.
 
-### 3. Build ICU
-1. Download and extract the [ICU source
-code](http://site.icu-project.org/download) to a folder named `icu` in the same
-directory as the other Swift project repositories (tested with ICU versions 55.1 and 59.1).
-1. Open `src/win32/allinone.sln` in Visual Studio.
-1. Make sure to select the correct architecture from the drop-down in Visual
-Studio.
-1. Right click on the solution in the Solution Explorer window and select
-"Build Solution".
-1. When this is done, add the `<icu-source>/bin` folder to your `Path`
-environment variable.
+### 3. Acquire ICU
+1. Download ICU from [ICU Project](http://site.icu-project.org) for Windows x64 and extract the binaries.
+1. Add the `bin64` folder to your `Path` environment variable.
 
 ### 4. Get ready
 - From within a **developer** command prompt (not PowerShell nor cmd, but [the
@@ -103,10 +96,7 @@ pushd "%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"
 cmake -G "Ninja"^
  -DLLVM_ENABLE_ASSERTIONS=TRUE^
  -DCMAKE_BUILD_TYPE=Debug^
- -DLLVM_TOOL_SWIFT_BUILD=NO^
- -DLLVM_INCLUDE_DOCS=TRUE^
  -DLLVM_ENABLE_PROJECTS=clang^
- -DLLVM_LIT_ARGS=-sv^
  -DLLVM_TARGETS_TO_BUILD=X86^
  -DLLVM_DEFAULT_TARGET_TRIPLE=x86_64-unknown-windows-msvc^
  "%swift_source_dir%/llvm"
@@ -131,29 +121,25 @@ mkdir "%swift_source_dir%/build/Ninja-DebugAssert/swift-windows-amd64"
 pushd "%swift_source_dir%/build/Ninja-DebugAssert/swift-windows-amd64"
 cmake -G "Ninja"^
  -DCMAKE_BUILD_TYPE=Debug^
- -DSWIFT_PATH_TO_CMARK_SOURCE="%swift_source_dir%/cmark"^
- -DSWIFT_PATH_TO_CMARK_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/cmark-windows-amd64"^
- -DSWIFT_CMARK_LIBRARY_DIR="%swift_source_dir%/build/Ninja-DebugAssert/cmark-windows-amd64/src"^
- -DSWIFT_PATH_TO_LLVM_SOURCE="%swift_source_dir%/llvm"^
- -DSWIFT_PATH_TO_LLVM_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
- -DSWIFT_PATH_TO_CLANG_SOURCE="%swift_source_dir%/llvm/tools/clang"^
- -DSWIFT_PATH_TO_CLANG_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
- -DICU_WINDOWS_x86_64_UC_INCLUDE="%swift_source_dir%/icu/include"^
- -DICU_WINDOWS_x86_64_UC_LIBRARY="%swift_source_dir%/icu/lib64/icuuc.lib"^
- -DICU_WINDOWS_x86_64_I18N_INCLUDE="%swift_source_dir%/icu/include"^
- -DICU_WINDOWS_x86_64_I18N_LIBRARY="%swift_source_dir%/icu/lib64/icuin.lib"^
- -DSWIFT_INCLUDE_DOCS=FALSE^
- -DSWIFT_INCLUDE_TESTS=FALSE^
  -DCMAKE_C_COMPILER="%llvm_bin_dir%/clang-cl.exe"^
  -DCMAKE_CXX_COMPILER="%llvm_bin_dir%/clang-cl.exe"^
- -DCMAKE_C_FLAGS="/Z7"^
- -DCMAKE_CXX_FLAGS="/Z7 -Wno-c++98-compat -Wno-c++98-compat-pedantic"^
+ -DSWIFT_PATH_TO_CMARK_SOURCE="%swift_source_dir%/cmark"^
+ -DCMAKE_CXX_FLAGS="-Wno-c++98-compat -Wno-c++98-compat-pedantic"^
  -DCMAKE_EXE_LINKER_FLAGS:STRING="/INCREMENTAL:NO"^
- -DCMAKE_MODULE_LINKER_FLAGS="/INCREMENTAL:NO"^
  -DCMAKE_SHARED_LINKER_FLAGS="/INCREMENTAL:NO"^
- -DCMAKE_STATIC_LINKER_FLAGS="/INCREMENTAL:NO"^
+ -DSWIFT_INCLUDE_DOCS=NO^
+ -DSWIFT_PATH_TO_LLVM_SOURCE="%swift_source_dir%/llvm"^
+ -DSWIFT_PATH_TO_CLANG_SOURCE="%swift_source_dir%/clang"^
+ -DSWIFT_PATH_TO_LIBDISPATCH_SOURCE="%swift_source_dir%/swift-corelibs-libdispatch"^
+ -DSWIFT_PATH_TO_LLVM_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
+ -DSWIFT_PATH_TO_CLANG_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
+ -DSWIFT_PATH_TO_CMARK_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/cmark-windows-amd64"^
+ -DSWIFT_WINDOWS_x86_64_ICU_UC_INCLUDE="%swift_source_dir%/icu/include"^
+ -DSWIFT_WINDOWS_x86_64_ICU_UC="%swift_source_dir%/icu/lib64/icuuc.lib"^
+ -DSWIFT_WINDOWS_x86_64_ICU_I18N_INCLUDE="%swift_source_dir%/icu/include"^
+ -DSWIFT_WINDOWS_x86_64_ICU_I18N="%swift_source_dir%/icu/lib64/icuin.lib"^
  -DCMAKE_INSTALL_PREFIX="C:/Program Files (x86)/Swift"^
-  "%swift_source_dir%/swift"
+ "%swift_source_dir%/swift"
 popd
 cmake --build "%swift_source_dir%/build/Ninja-DebugAssert/swift-windows-amd64"
 ```