configs: replace powerpc64le with ppc64le in the %_host_cpu macro

In older RPM versions, the `%_host_cpu` macro was not correctly set for
the `ppc64le` architecture.  Let's work around this issue in Mock.

This problem arises because RPM determines the per-distribution value of
the `%_host_cpu` macro at its build time (rpm.rpm package).  The value
is provided by the build system, from the build environment analysis.

Older RPM versions use the `config.guess` script (file copy from the
Automake package) for this purpose.  However, even as of 2024, this
script still returns an incorrect architecture string on ppc64le boxes:

    $ /usr/lib/rpm/redhat/config.guess
    powerpc64le-unknown-linux-gnu
    ^^^^^^^^^^^

Newer versions of RPM (v4.19+ in Fedora 39+ and EL 10+) use the CMake
build system, which sets the correct `%_host_cpu` value `ppc64le`.

This commit addresses the issue by overriding the macro in older chroots
(RPM v4.18 and earlier).  This is what the Fedora Koji build system has
been doing for **all** `ppc64le` Mock chroots for a long time—now, it's
being applied for Mock users in `mock-core-configs`.

The `%_host_cpu` macro is used by `/bin/rpmbuild` when validating
architectures, especially with the `ExclusiveArch/ExcludeArch` checks
for `BuildArch: noarch` packages.  Maintainers sometimes do:

    BuildArch: noarch
    ExcludeArch: %java_arches

However, since `%java_arches` doesn't include the "non-standard"
`powerpc64le` architecture string (and no other "similar" macro does,
including the more extensive ones like `%go_arches`), builds in Mock can
fail early with the error:

    error: Architecture is not included: powerpc64le
    Building target platforms: ppc64le
    Building for target ppc64le

This happens because:

    $ rpm --eval %java_arches
    aarch64 ppc64le s390x x86_64
    $ rpm --eval %_host_cpu
    powerpc64le

The arch-specific packages care about `%_target_cpu` value (which seems
valid everywhere) so they don't suffer from this problem.  The 'noarch'
are affected because of the `%_target_cpu → %_host_cpu` fallback:

    https://github.com/rpm-software-management/rpm/blob/21457de886faf2415500a8bb7cc6c816d72939ef/build/parsePreamble.c#L442-L449

And given by fact that the `%_build_cpu` macro is just `%_host_cpu`:

    $ rpm --showrc | grep build_cpu
    -13: _build_cpu %{_host_cpu}

Relates: fedora-copr/copr#2870
Relates: https://bugzilla.redhat.com/show_bug.cgi?id=1461288

mock-core-configs/etc/mock/centos-stream+epel-8-ppc64le.cfg

@@ -6,3 +6,5 @@ config_opts['root'] = 'centos-stream+epel-8-ppc64le'
 config_opts['description'] = 'CentOS Stream 8 + EPEL'
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/centos-stream+epel-9-ppc64le.cfg

@@ -6,3 +6,5 @@ config_opts['root'] = 'centos-stream+epel-9-ppc64le'
 config_opts['description'] = 'CentOS Stream 9 + EPEL'
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/centos-stream+epel-next-8-ppc64le.cfg

@@ -8,3 +8,5 @@ config_opts['root'] = 'centos-stream+epel-next-8-ppc64le'
 config_opts['description'] = 'CentOS Stream 8 + EPEL Next'
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/centos-stream+epel-next-9-ppc64le.cfg

@@ -7,3 +7,5 @@ config_opts['root'] = 'centos-stream+epel-next-9-ppc64le'
 config_opts['description'] = 'CentOS Stream 9 + EPEL Next'
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/centos-stream-8-ppc64le.cfg

@@ -5,3 +5,5 @@ config_opts['root'] = 'centos-stream-8-ppc64le'
 config_opts['description'] = 'CentOS Stream 8'
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/centos-stream-9-ppc64le.cfg

@@ -4,3 +4,5 @@ include('templates/centos-stream-9.tpl')
 config_opts['root'] = 'centos-stream-9-ppc64le'
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/rhel-7-ppc64le.cfg

@@ -4,3 +4,5 @@ config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
 
 config_opts['rhel_product'] = 'power-le'
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/rhel-8-ppc64le.cfg

@@ -2,3 +2,5 @@ include('templates/rhel-8.tpl')
 
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

mock-core-configs/etc/mock/rhel-9-ppc64le.cfg

@@ -2,3 +2,5 @@ include('templates/rhel-9.tpl')
 
 config_opts['target_arch'] = 'ppc64le'
 config_opts['legal_host_arches'] = ('ppc64le',)
+# see pull-request #1195
+config_opts['macros']['%_host_cpu'] = 'ppc64le'

releng/release-notes-next/ppc64le-not-powerpc64le-host-cpu.config

@@ -0,0 +1,13 @@
+We [updated the configuration][PR#1195] files for chroots that still use older
+RPM versions (v4.18 and earlier), which affects RHEL/CentOS 9 and older.  These
+older RPM versions were built with an incorrect default for the `%_host_cpu`
+macro in `ppc64le` chroots, where the macro incorrectly resolved to
+`powerpc64le` instead of `ppc64le`.
+
+This incorrect value caused issues during architecture validation, such as when
+checking `ExclusiveArch: ppc64le` for `BuildArch: noarch` packages (done
+in-chroot by `/bin/rpmbuild`).
+
+The incorrect macro value has now been overridden in the relevant `ppc64le`
+configuration files in Mock, ensuring that `ExcludeArch` and `ExclusiveArch`
+validations resolve correctly.