[build2] Patches for C++23 std::aligned_storage and libpkgconf v1.9.0+

[Matthew Krupcale]

Hello,

On Fedora 38 and 39 there were some bugs [1,2] reported regarding
failure to build or install, respectively, build2 v0.15.0. I've got
things building again in a Copr [3] before I push changes to official
repos with three patches [4-6] addressing the update of git to v2.38+,
deprecation of std::aligned_storage in C++23 [7], and the update of
libpkgconf to v1.9.4 [8]. The former patch is already upstream [9],
while the second patch I'm not 100% certain about since I don't know
what the alignment should be in all the build2 use cases since the
template Align parameter was unspecified. The final patch is to
address a change in the libpkgconf error handler function signature
[10].

If there's a better solution to these latter two issues, let me know,
and I can adjust the patches as necessary before I push to official
repos.

Best,
Matthew

[1] https://bugzilla.redhat.com/show_bug.cgi?id=2171452
[2] https://bugzilla.redhat.com/show_bug.cgi?id=2172682
[3] https://copr.fedorainfracloud.org/coprs/mkrupcale/build2/build/5566244/
[4] https://copr-dist-git.fedorainfracloud.org/cgit/mkrupcale/build2/build2.git/plain/bpkg-git-v2.38.patch?h=f38
[5] https://copr-dist-git.fedorainfracloud.org/cgit/mkrupcale/build2/build2.git/plain/libbuild2-cxx23-aligned_storage-deprecation.patch?h=f38
[6] https://copr-dist-git.fedorainfracloud.org/cgit/mkrupcale/build2/build2.git/plain/libbuild2-libpkgconf-error_handler-non-const-data.patch?h=f38
[7] https://en.cppreference.com/w/cpp/types/aligned_storage
[8] https://bodhi.fedoraproject.org/updates/FEDORA-2023-119540e472
[9] https://git.build2.org/cgit/bpkg/commit/?id=a97b12a027546b37f66d3e08064f92f5539cf79e
[10] https://github.com/pkgconf/pkgconf/commit/f5d6bb71f84ff8acdea0eb08f6bd41b5c8acc1f0