[gentoo-portage-dev] Fixing EAPI 8 --enable-static once and for all

[David Seifert <soap@gentoo.org>]

Attached a patch to finally fix https://bugs.gentoo.org/814380.

When I opened the bug, it was clear that I intended to only disable
static libtool archive building. Unfortunately, I hadn't done the
necessary due diligence, and it turns out how we detect the
"--enable-static" flag is overly broad and leads to a sizable number of
false positives in EAPI 8.

I have 937 EAPI 8 packages on my machine, and in 0 cases does my patch
now produce static libraries where none were produced before, while it
successfully reduces the annoying QA warnings on packages that don't use
libtool or use the flag for different purposes:

1. packages that have an "off-target"/false-positive flag triggering
   the current logic:

  dev-libs/nspr-4.35
    --enable-static-rtl     Use the MSVC static runtime library
  sys-fs/lvm2-2.03.16
    --enable-static_link    use this to link the tools to their libraries

2. packages with a real --{dis,en}able-static flag, but with semantics
   that don't actually disable building of static-libs:

  dev-util/strace-5.19
    --enable-static         link strace statically
  sys-process/htop-3.2.1
    --enable-static         build a static htop binary [default=no]
  media-video/mkvtoolnix-71.1.0
    --enable-static         make a static build of the applications (no)
    --enable-static-qt      link to static versions of the Qt library (no)

dev-util/strace has a $(use_enable static) option, and the other two are
default disabled. Hence in all of these cases, the patch does not change
the build output.

3. packages with a --{dis,en}able-static flag that controls building of
   static libraries, but with a slightly different --help output that
   doesn't trigger the updated glob anymore:

  dev-libs/icu-72.1
    --enable-static         build static libraries default=no
  dev-libs/nettle-3.8.1
    --disable-static        Do not build any static library
  net-print/cups-2.4.2
    --enable-static         install static libraries

All of these packages pass a $(use_enable static-libs static) option,
hence none of them would be affected by the missing --disable-static.

With this extensive analysis, I believe this patch to be safe.