CMake: add Observation dependency to libraries that import Foundation...

when building for Apple platforms.

In this scenario we are not building our own Foundation,
but we are importing the one from the underlying SDK -- this in turns
requires Observation, which is something we typically build.

Addresses rdar://162286123

Author: edymtt

stdlib/private/StdlibUnicodeUnittest/CMakeLists.txt

@@ -1,5 +1,11 @@
 set(swift_stdlib_unittest_compile_flags)
 
+if(SWIFT_ENABLE_EXPERIMENTAL_OBSERVATION)
+  # This library imports Foundation from the SDK, which re-exports
+  # Observation which is part of this build.
+  list(APPEND swift_stdlib_unicode_unittest_darwin_dependencies Observation)
+endif()
+
 add_swift_target_library(swiftStdlibUnicodeUnittest ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
   # This file should be listed the first.  Module name is inferred from the
   # filename.
@@ -10,6 +16,12 @@ add_swift_target_library(swiftStdlibUnicodeUnittest ${SWIFT_STDLIB_LIBRARY_BUILD
   WordBreaking.swift
 
   SWIFT_MODULE_DEPENDS StdlibUnittest
+  SWIFT_MODULE_DEPENDS_IOS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_OSX ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_TVOS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_WATCHOS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_XROS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_MACCATALYST ${swift_stdlib_unicode_unittest_darwin_dependencies}
   SWIFT_MODULE_DEPENDS_ANDROID Android
   SWIFT_MODULE_DEPENDS_LINUX Glibc
   SWIFT_MODULE_DEPENDS_LINUX_STATIC Musl

stdlib/private/StdlibUnittest/CMakeLists.txt

@@ -9,6 +9,12 @@ if((SWIFT_BUILD_CLANG_OVERLAYS
   list(APPEND swift_stdlib_unittest_darwin_dependencies _Builtin_float)
 endif()
 
+if(SWIFT_ENABLE_EXPERIMENTAL_OBSERVATION)
+  # This library imports Foundation from the SDK, which re-exports
+  # Observation which is part of this build.
+  list(APPEND swift_stdlib_unittest_darwin_dependencies Observation)
+endif()
+
 set(swift_stdlib_unittest_compile_flags
   "-Xfrontend" "-disable-objc-attr-requires-foundation-module")
 

stdlib/private/StdlibUnittestFoundationExtras/CMakeLists.txt

@@ -1,9 +1,21 @@
+if(SWIFT_ENABLE_EXPERIMENTAL_OBSERVATION)
+  # This library imports Foundation from the SDK, which re-exports
+  # Observation which is part of this build.
+  list(APPEND swift_stdlib_unittest_foundationextras_darwin_dependencies Observation)
+endif()
+
 add_swift_target_library(swiftStdlibUnittestFoundationExtras ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
   # This file should be listed the first.  Module name is inferred from the
   # filename.
   StdlibUnittestFoundationExtras.swift
   UnavailableFoundationMethodThunks.mm
 
+  SWIFT_MODULE_DEPENDS_IOS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_OSX ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_TVOS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_WATCHOS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_XROS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_MACCATALYST ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
   SWIFT_MODULE_DEPENDS StdlibUnittest
   SWIFT_COMPILE_FLAGS ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
   INSTALL_IN_COMPONENT stdlib-experimental