[cmake] Build Swift host libraries with -DCLANG_BUILD_STATIC on Windows

By default (`CLANG_BUILD_STATIC` and `CLANG_EXPORTS` not defined) some
Clang visibility macros expand to `__declspec(dllimport)`. Swift depends
on Clang statically, so needs to turn these macros off.

Author: AnthonyLatsis

cmake/modules/AddSwift.cmake

@@ -269,6 +269,16 @@ function(_add_host_variant_c_compile_flags target)
       target_compile_options(${target} PRIVATE
         $<$<COMPILE_LANGUAGE:C,CXX,OBJC,OBJCXX>:-U_DEBUG>)
     endif()
+
+    # Swift host libraries are always linked with Clang libraries statically,
+    # so turn off Clang visibility macros for both the library and its
+    # consumers.
+    #target_compile_definitions(${target} PUBLIC
+    #  $<$<COMPILE_LANGUAGE:C,CXX,OBJC,OBJCXX>:CLANG_BUILD_STATIC>)
+    #if(TARGET "obj.${target}")
+    #  target_compile_definitions("obj.${target}" PUBLIC
+    #    $<$<COMPILE_LANGUAGE:C,CXX,OBJC,OBJCXX>:CLANG_BUILD_STATIC>)
+    #endif()
   endif()
 
   if(SWIFT_HOST_VARIANT_SDK STREQUAL "ANDROID")

lib/APIDigester/CMakeLists.txt

@@ -7,4 +7,9 @@ add_swift_host_library(swiftAPIDigester STATIC
 target_link_libraries(swiftAPIDigester PRIVATE
   swiftIDE)
 
+target_link_libraries(swiftAPIDigester INTERFACE
+  clangAST
+  clangLex
+  clangSema)
+
 set_swift_llvm_is_available(swiftAPIDigester)