Fix blfs tools Makefile now that MAKEFLAGS is set

Previously, the "update" target was just added to the end of
the "all" target prerequisites, so that it was run at the end.
But now, we enter make with some -j value in MAKEFLAGS, so that
the "update" target may well be run before the other targets, which
is wrong: for example if it is run before the "xxx-z-libxslt" target,
xsltproc is not found and the update target fails.
To fix, define "update" as the default target, and have it depend
on "all".

common/libs/func_install_blfs

@@ -218,10 +218,10 @@ pushd $BUILDDIR$BLFS_ROOT/work
 # installation, using libxslt, which is not installed yet. So move
 # updating to the end of the process, adding an 'update' target
 sed -i -e '/xsltproc/,+6d' \
-       -e '/^all/s@$@ update@' \
+       -e '/^all/i update:' \
        -e 's/touch/@touch/' Makefile
 cat >> Makefile << EOF
-update:
+update: all
 	@echo Updating the tracking file
 	@for pack in \$\$(grep '<productname' ../$LFS_XML/tmp/lfs-full.xml | \\
 		sed 's/.*>\([^<]*\)<.*/\1/' | \\