Add temporary 'SwiftCompatibilitySpan 6.2' availability macro

Author: slavapestov

test/lit.cfg

@@ -502,7 +502,7 @@ def availability_macro_to_swift_abi_target_triple(macro):
     # Use a regex and split to pull out the components of an availability macro
     # that is formatted like this:
     #    SwiftStdlib 5.0:macOS 10.14.4, iOS 12.2, watchOS 5.2, tvOS 12.2
-    matches = re.search(r'^[\s]*SwiftStdlib[\s]+([0-9\.]+)[\s]*:[\s]*(.+)', macro)
+    matches = re.search(r'^[\s]*Swift(?:Stdlib|CompatibilitySpan)[\s]+([0-9\.]+)[\s]*:[\s]*(.+)', macro)
     stdlib_vers = matches.group(1)
     vers_by_platform = {}
     for platform_vers in matches.group(2).split(', '):

utils/availability-macros.def

@@ -38,6 +38,11 @@ SwiftStdlib 5.10:macOS 14.4, iOS 17.4, watchOS 10.4, tvOS 17.4, visionOS 1.1
 SwiftStdlib 6.0:macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0
 SwiftStdlib 6.1:macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, visionOS 9999
 SwiftStdlib 6.2:macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, visionOS 9999
+
+# Note: This cannot be 9999, so use the last non-placeholder entry instead.
+# This will go away once 'SwiftStdlib 6.2' is filled in.
+SwiftCompatibilitySpan 6.2:macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0
+
 # TODO: When you add a new version, remember to tell the compiler about it
 # by also adding it to include/swift/AST/RuntimeVersions.def.