caches: add a cache for building just the runtime on Windows

This allows configuration of a build for just the runtime/SDK components
rather than a complete toolchain.  It allows for more effective
iteration when working on just the runtime aspect of the toolchain.

Author: compnerd

cmake/caches/Runtime-Windows-x86_64.cmake

@@ -0,0 +1,20 @@
+
+set(SWIFT_HOST_VARIANT_SDK WINDOWS CACHE STRING "")
+set(SWIFT_HOST_VARIANT_ARCH x86_64 CACHE STRING "")
+
+# NOTE(compnerd) disable the tools, we are trying to build just the standard
+# library.
+set(SWIFT_INCLUDE_TOOLS NO CACHE BOOL "")
+
+# NOTE(compnerd) cannot build tests since the tests require the toolchain
+set(SWIFT_INCLUDE_TESTS NO CACHE BOOL "")
+
+# NOTE(compnerd) cannot build docs since that requires perl
+set(SWIFT_INCLUDE_DOCS NO CACHE BOOL "")
+
+# NOTE(compnerd) these are part of the toolchain, not the runtime.
+set(SWIFT_BUILD_SYNTAXPARSERLIB NO CACHE BOOL "")
+set(SWIFT_BUILD_SOURCEKIT NO CACHE BOOL "")
+
+# NOTE(compnerd) build with the compiler specified, not a just built compiler.
+set(SWIFT_BUILD_RUNTIME_WITH_HOST_COMPILER YES CACHE BOOL "")