MFC: r276052,r276053

Build selective portions of gnu/usr.bin/texinfo as part of build-tools to
ensure that building on a host without makeinfo (i.e. a host where
make delete-old -DWITHOUT_INFO was run), then building with MK_INFO == yes
doesn't manifest in build errors when building info pages

This manifested itself like the following when I was build testing an MFC
change on stable/10:

makeinfo --no-split -I /usr/src/gnu/lib/libregex/doc -I /usr/src/gnu/lib/libregex/doc regex.texi  -o regex.info
makeinfo: not found
*** [regex.info] Error code 127

make[6]: stopped in /usr/src/gnu/lib/libregex/doc
1 error