Remove underscores from CFBundleIdentifier of libraries.

Underscores aren't permitted in these identifiers.
Fixes rdar://84645973.

Author: DougGregor

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -1263,7 +1263,9 @@ function(add_swift_target_library_single target name)
   set(PLIST_INFO_PLIST "Info.plist" CACHE STRING "Plist name")
   if("${SWIFTLIB_SINGLE_SDK}" IN_LIST SWIFT_DARWIN_PLATFORMS AND SWIFTLIB_SINGLE_IS_STDLIB)
     set(PLIST_INFO_NAME ${name})
-    set(PLIST_INFO_UTI "com.apple.dt.runtime.${name}")
+
+    # Underscores aren't permitted in the bundle identifier.
+    string(REPLACE "_" "" PLIST_INFO_UTI "com.apple.dt.runtime.${name}")
     set(PLIST_INFO_VERSION "${SWIFT_VERSION}")
     if (SWIFT_COMPILER_VERSION)
       set(PLIST_INFO_BUILD_VERSION