build: work around issues between pkg_rpm and rpmbuild after 4.20 (#4652

)

Since rpmbuild v4.20, the _builddir variable is forcefully set to
<chosen_builddir>/<pkg_name> (which is created if it doesn't exist). Any
files that are not built/copied by the %prep% phase must be already
present in <chosen_builddir>/<pkg_name>/[%buildsubdir].

pkg_rpm doesn't expect that and places the files to be packaged in
<chosen_builddir>. Since %buildsubdir is not used (=="."), we compensate
by setting it to "..". As a result
<chosen_builddir>/<pkg_name>/[%buildsubdir] evaluates to
<chosen_buildir> thereby restoring pre-4.20 behavior.

Since 4.20, debug-info rpms are built by default. We don't support or
want that, so we now set "don't-do-it" explicitly.

Fixes #4653

dist/package.bzl

@@ -121,6 +121,17 @@ def scion_pkg_rpm(name, package, executables = {}, systemds = [], configs = [],
     if post:
         kwargs.pop("postinst")
 
+    # defines are work-arounds for pkg_rpm issues:
+    # _smp_build_ncpus: used to be default.
+    # buildsubdir: starting with rpmbuild 4.20, builddir is forcefully replaced with:
+    #              <chosen_builddir>/<package_name> (which is created if it doesn't exist).
+    #              pkg_rpm assumes that one can place ready-to-package files directly into
+    #              <chosen_builddir>, we need <builddir>/<buildsubdir> to evealuate as
+    #              <chosen_buidldir>. Hence the "buildsubdir=..". It's a hack. Check if later
+    #              versions of pkg_rpm fix that.
+    # debug_package: Starting with rpmbuild 4.20, debug-info packages are built by default. We
+    #                currently don't want that and our binaries do not have the required symbols.
+
     pkg_rpm(
         name = name,
         summary = kwargs["description"],
@@ -132,9 +143,10 @@ def scion_pkg_rpm(name, package, executables = {}, systemds = [], configs = [],
         package_name = package,
         release = "%autorelease",
         version_file = ":%s_version" % name,
-        defines = {"_smp_build_ncpus": "1"},
+        defines = {"_smp_build_ncpus": "1", "buildsubdir": "..", "debug_package": "%{nil}"},
         requires = deps,
         post_scriptlet_file = post,
+        source_date_epoch = 0,
         **kwargs
     )