Add the distribution tag to -print-target-info

Ideally this would also update the `--version` output to be overridden
by `SWIFT_TOOLCHAIN_VERSION`, but unfortunately various tools rely on
the current format (eg. swift-build).

(cherry picked from commit 3c098782b4)

lib/Basic/Version.cpp

@@ -304,17 +304,9 @@ StringRef getSwiftRevision() {
 #endif
 }
 
-bool isCurrentCompilerTagged() {
-#ifdef SWIFT_COMPILER_VERSION
-  return true;
-#else
-  return false;
-#endif
-}
-
 StringRef getCurrentCompilerTag() {
-#ifdef SWIFT_COMPILER_VERSION
-  return SWIFT_COMPILER_VERSION;
+#ifdef SWIFT_TOOLCHAIN_VERSION
+  return SWIFT_TOOLCHAIN_VERSION;
 #else
   return StringRef();
 #endif