let configure recognize Alphas

llvm-svn: 19811
diff --git a/llvm/autoconf/configure.ac b/llvm/autoconf/configure.ac
index 1102bf9..39e812a 100644
--- a/llvm/autoconf/configure.ac
+++ b/llvm/autoconf/configure.ac
@@ -174,6 +174,7 @@
   amd64-* | x86_64-*)     llvm_cv_target_arch="x86_64" ;;
   sparc*-*)               llvm_cv_target_arch="Sparc" ;;
   powerpc*-*)             llvm_cv_target_arch="PowerPC" ;;
+  alpha*-*)               llvm_cv_target_arch="Alpha" ;;
   *)                      llvm_cv_target_arch="Unknown" ;;
 esac])