Enable --arch option in run-test.sh (#24300)

There is a help message for --arch option,
but there is no code for the option.

Signed-off-by: Hyung-Kyu Choi <hk0110.choi@samsung.com>

Author: hqueue

run-test.sh

@@ -31,7 +31,7 @@ usage()
     echo "                                      default: Debug"
     echo "    --os <os>                         OS to run (FreeBSD, Linux, NetBSD or OSX)"
     echo "                                      default: detect current OS"
-    echo "    --arch <Architecture>             Architecture to run (x64, arm, x86, arm64)"
+    echo "    --arch <Architecture>             Architecture to run (x64, arm, armel, x86, arm64)"
     echo "                                      default: detect current architecture"
     echo
     echo "Execution options:"
@@ -304,6 +304,9 @@ do
         --os)
         OS=$2
         ;;
+        --arch)
+        __Arch=$2
+        ;;
         --coreclr-coverage)
         CoreClrCoverage=ON
         ;;