configure: Don't check for an unsupported version of LLVM (#22449)

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m4/find_llvm_prog.m4

@@ -11,7 +11,7 @@
 #
 AC_DEFUN([FIND_LLVM_PROG],[
     # Test for program with and without version name.
-    PROG_VERSION_CANDIDATES=$(for llvmVersion in `seq $4 -1 $3`; do echo "$2-$llvmVersion $2-$llvmVersion.0 $2$llvmVersion"; done)
+    PROG_VERSION_CANDIDATES=$(for llvmVersion in `seq $(($4-1)) -1 $3`; do echo "$2-$llvmVersion $2-$llvmVersion.0 $2$llvmVersion"; done)
     AC_CHECK_TOOLS([$1], [$PROG_VERSION_CANDIDATES $2], [])
     AS_IF([test x"$$1" != x],[
         PROG_VERSION=`$$1 --version | awk '/.*version [[0-9\.]]+/{for(i=1;i<=NF;i++){ if(\$i ~ /^[[0-9\.]]+$/){print \$i}}}'`