Missing --tag=CC for libtool

[Aleksey Cheusov <cheusov%tut.by@localhost>]

From time to time I see package failures caused by missing --tag=CC
option in libtool. I saw such failures on NetBSD, Linux and even
cross-compiling bulk builds I ran recently.

Example:
http://mova.org/~cheusov/pub/pkgsrc-distbb/NetBSD-sparc64/current/logs/cross-test3p1/textproc_expat_expat-2.0.1nb2/stage_build.html

In my view it is very annoying to patch packages where such failures
occure and requires man * months for working on this kind of issues.

LIBTOOL is passed to the build program like this

   .if defined(USE_LIBTOOL)
   LIBTOOL_REQD?=<><------>2.2.6bnb3
   
BUILD_DEPENDS+=><------>libtool-base>=${_OPSYS_LIBTOOL_REQD:U${LIBTOOL_REQD}}:../../devel/
   CONFIGURE_ENV+=><------>LIBTOOL="${LIBTOOL} ${LIBTOOL_FLAGS}"
   MAKE_ENV+=<----><------>LIBTOOL="${LIBTOOL} ${LIBTOOL_FLAGS}"
   .endif

Can we add --tag=CC to LIBTOOL_FLAGS variable
if USE_LANGUAGES is set to "c"?

-- 
Best regards, Aleksey Cheusov.