builddep: Conditional build-dependcies ignores --forcearch

[ppisar]

Running:

dnf5 --repo=rawhide --use-host-config --installroot=/tmp/i builddep --forcearch=aarch64 ~test/rpmbuild/SPECS/test.spec

on x86_64 host where the spec file has a conditional dependency:

BuildRequires:  glibc
%ifarch aarch64
BuildRequires:  dontpanic
%endif

Does not install "dontpanic":

Package                          Arch       Version                          Repository            Size
Installing:
 glibc                           aarch64    2.40.9000-23.fc42                rawhide            6.2 MiB
Installing dependencies:
 basesystem                      noarch     11-21.fc41                       rawhide            0.0   B
 bash                            aarch64    5.2.37-1.fc42                    rawhide            8.2 MiB
 fedora-gpg-keys                 noarch     42-0.3                           rawhide          126.4 KiB
 fedora-release                  noarch     42-0.11                          rawhide            0.0   B
 fedora-release-common           noarch     42-0.11                          rawhide           19.8 KiB
 fedora-release-identity-basic   noarch     42-0.11                          rawhide          719.0   B
 fedora-repos                    noarch     42-0.3                           rawhide            4.9 KiB
 fedora-repos-rawhide            noarch     42-0.3                           rawhide            2.2 KiB
 filesystem                      aarch64    3.18-29.fc42                     rawhide          106.0   B
 glibc-common                    aarch64    2.40.9000-23.fc42                rawhide            1.3 MiB
 glibc-minimal-langpack          aarch64    2.40.9000-23.fc42                rawhide            0.0   B
 libgcc                          aarch64    14.2.1-6.fc42                    rawhide          222.2 KiB
 ncurses-base                    noarch     6.5-2.20240629.fc41              rawhide          326.3 KiB
 ncurses-libs                    aarch64    6.5-2.20240629.fc41              rawhide            2.2 MiB
 setup                           noarch     2.15.0-5.fc41                    rawhide          720.7 KiB

It seems that the spec file is not expanded with the overridden architecture.
Maybe it opens a worm of cans because the expansion uses host librpm with host macro definitions.

Downstream bug report https://bugzilla.redhat.com/show_bug.cgi?id=2122520.

dnf5-5.2.8.1-2.fc42.x86_64 is affected.