Architecture applicability check performed very late by rpm 4.20.0

[jpalus]

Describe the bug
Architecture applicability check is not performed early in the process by rpmbuild but very late after successful %install.

To Reproduce
Steps to reproduce the behavior:

1. Sample spec file:

Summary:	test
Name:		test
Version:	1
Release:	1
License:	GPL
Group:		Applications/System
ExclusiveArch:	x86_64

%description
test

%prep
echo prep

%build
echo build

%install
echo install

%clean
rm -rf $RPM_BUILD_ROOT

2. rpmbuild -bb test.spec (on arch different than x86_64 ie aarch64 or with different --target)
3. %mkbuilddir, %prep, %build and %install are all executed and only then error: Architecture is not included: aarch64 appears

Expected behavior
rpmbuild fails with error: Architecture is not included: aarch64 before even %mkbuilddir is executed.

Environment

• OS / Distribution: PLD Linux 3.0
• Version rpm 4.20.0

Additional context
Appears to be caused by this change: fd32a43 which made checkForValidArchitectures() part of finalizeSpec() invoked through parseGeneratedSpecs() only after successful %install

[pmatilai]

This seems like a regression indeed, caused by the delayed sanity checking for the dynamic spec generation stuff. But buildarch compatibility pretty obviously has to be decided up front, not after the build...

Thanks for reporting!