Use correct cflags for kvm-kmod when cross compiling

Using $pkgconfig instead of pkg-config will use
${cross_prefix}pkg-config if that is available.

This fix is needed for cross compilations without
modified PATH. Without the fix, PATH must be modified
to find the cross pkg-config before the native
pkg-config.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

configure

@@ -1488,7 +1488,7 @@ EOF
             kvm_cflags="$kvm_cflags -I$kerneldir/arch/$cpu/include"
       fi
   else
-    kvm_cflags=`pkg-config --cflags kvm-kmod 2> /dev/null`
+    kvm_cflags=`$pkgconfig --cflags kvm-kmod 2>/dev/null`
   fi
   if compile_prog "$kvm_cflags" "" ; then
     kvm=yes