Our getconf currently doesn't support LONG_BIT

--- elfutils-0.179/tests/run-large-elf-file.sh	2020-03-30 07:17:45.000000000 -0500
+++ elfutils-0.179/tests/run-large-elf-file.sh	2020-04-17 01:16:37.479546189 -0500
@@ -19,12 +19,14 @@
 
 # Only run on 64bit systems, 32bit systems don't support > 4GB
 # ELF files.
-long_bit=$(getconf LONG_BIT)
-echo "long_bit: $long_bit"
-if test $long_bit -ne 64; then
+case "$(uname -m)" in
+*64)
+  ;;
+*)
   echo "Only 64bit systems can create > 4GB ELF files"
   exit 77
-fi
+  ;;
+esac
 
 # These tests need lots of disk space since they test files > 4GB.
 # Skip if there just isn't enough (2.5 * 4 = 10GB).