Bump Coreutils minimal version to 8.1 and check for nproc

chapter02/hostreqs.xml

@@ -50,8 +50,9 @@
       должен быть ссылкой на bison или небольшой скрипт, запускающий bison)</para>
     </listitem>
 
+    <!-- In Coreutils-8.1 the nproc program is added.  -->
     <listitem>
-      <para><emphasis role="strong">Coreutils-7.0</emphasis></para>
+      <para><emphasis role="strong">Coreutils-8.1</emphasis></para>
     </listitem>
 
     <listitem>
@@ -212,8 +213,8 @@ ver_kernel()
    fi
 }
 
-# Coreutils first because-sort needs Coreutils >= 7.0
-ver_check Coreutils      sort     7.0 || bail "--version-sort unsupported"
+# Coreutils first because --version-sort needs Coreutils >= 7.0
+ver_check Coreutils      sort     8.1 || bail "Coreutils too old, stop"
 ver_check Bash           bash     3.2
 ver_check Binutils       ld       2.13.1
 ver_check Bison          bison    2.7
@@ -253,7 +254,13 @@ echo "Compiler check:"
 if printf "int main(){}" | g++ -x c++ -
 then echo "OK:    g++ works";
 else echo "ERROR: g++ does NOT work"; fi
-rm -f a.out</literal>
+rm -f a.out
+
+if [ "$(nproc)" = "" ]; then
+   echo "ERROR: nproc is not available or it produces empty output"
+else
+   echo "OK: nproc reports $(nproc) logical cores are available"
+fi</literal>
 EOF
 
 bash version-check.sh</userinput></screen>