add bc, required for new linux kernels

README

@@ -22,6 +22,7 @@ Before you can start you need to install some tools:
 - ncurses5 headers
 - zlib headers
 - perl
+- bc
 
 There is a check for the required versions of these tools in advance, though.
 (to re-issue the checks, use "make prereq").

scripts/scan-tools.sh

@@ -237,6 +237,12 @@ if ! which pkg-config >/dev/null 2>&1; then
 	out=1
 fi
 
+if ! which bc >/dev/null 2>&1; then
+	echo  "You need bc to continue."
+	echo
+	out=1
+fi
+
 cd $topdir
 rm -rf tmp