simplify lldb build instructions

Update the LLDB build instructions for windows to be simpler and use MSVC to build.  This is just as effective and has the benefit of making it easier to debug lldb.

Author: compnerd

docs/WindowsBuild.md

@@ -166,17 +166,13 @@ pushd "%swift_source_dir%/build/Ninja-DebugAssert/lldb-windows-amd64"
 cmake -G "Ninja" "%swift_source_dir%/lldb"^
   -DCMAKE_BUILD_TYPE=Debug^
   -DLLDB_PATH_TO_CMARK_SOURCE="%swift_source_dir%/cmark"^
-  -DLLDB_PATH_TO_CMARK_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/cmark-windows-amd64"^
   -DLLDB_PATH_TO_LLVM_SOURCE="%swift_source_dir%/llvm"^
-  -DLLDB_PATH_TO_LLVM_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
   -DLLDB_PATH_TO_CLANG_SOURCE="%swift_source_dir%/clang"^
-  -DLLDB_PATH_TO_CLANG_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
   -DLLDB_PATH_TO_SWIFT_SOURCE="%swift_source_dir%/swift"^
+  -DLLDB_PATH_TO_CMARK_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/cmark-windows-amd64"^
+  -DLLDB_PATH_TO_CLANG_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
+  -DLLDB_PATH_TO_LLVM_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/llvm-windows-amd64"^
   -DLLDB_PATH_TO_SWIFT_BUILD="%swift_source_dir%/build/Ninja-DebugAssert/swift-windows-amd64"^
-  -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"^
   -DLLVM_ENABLE_ASSERTIONS=YES
 popd
 cmake --build "%swift_source_dir%/build/Ninja-RelWithDebInfoAssert/lldb-windows-amd64"