Inject linker script to generate package notes

https://fedoraproject.org/wiki/Changes/Package_information_on_ELF_objects
Macros are used only if defined. Definitions are provided in the
package-notes-srpm-macros, which is now Required (on Fedora).

buildflags.md

@@ -246,6 +246,22 @@ it is possible to add `-fcommon` to the flags by defining `%_legacy_common_suppo
 
 Properly fixing the failure is always preferred!
 
+### Package note on ELF objects
+
+A note that describes the package name, version, and architecture is
+inserted via a linker script (`%_package_note_file`). The script is
+generated when `%set_build_flags` is called. The linker option that
+injects the linker script is added to `%{build_ldflags}` via the
+`%{_package_note_flags}` macro.
+
+To opt out of the use of the linker script, include this in the spec file:
+
+    %undefine _package_note_flags
+
+To opt out of generation of the linker script, include this in the spec file:
+
+    %undefine _generate_package_note_file
+
 ### Post-build ELF object processing
 
 By default, DWARF debugging information is separated from installed

macros

@@ -72,7 +72,7 @@
 # When clang is used as a linker driver, it does not auto-detect the LTO
 # bytecode and neither does bfd, so we need to explicitly pass the -flto
 # flag when linking.
-%build_ldflags -Wl,-z,relro %{_ld_as_needed_flags} %{_ld_symbols_flags} %{_hardened_ldflags} %{_annotation_ldflags} %[ "%{toolchain}" == "clang" ? "%{?_lto_cflags}" : "" ] %{_build_id_flags}
+%build_ldflags -Wl,-z,relro %{_ld_as_needed_flags} %{_ld_symbols_flags} %{_hardened_ldflags} %{_annotation_ldflags} %[ "%{toolchain}" == "clang" ? "%{?_lto_cflags}" : "" ] %{_build_id_flags} %{?_package_note_flags}
 
 # Expands to shell code to set the compiler/linker environment
 # variables CFLAGS, CXXFLAGS, FFLAGS, FCFLAGS, LDFLAGS if they have
@@ -80,6 +80,7 @@
 # been set implicitly at the start of the %%build section.
 # LT_SYS_LIBRARY_PATH is used by libtool script.
 %set_build_flags \
+  %{?_generate_package_note_file} ; \
   CFLAGS="${CFLAGS:-%{build_cflags}}" ; export CFLAGS ; \
   CXXFLAGS="${CXXFLAGS:-%{build_cxxflags}}" ; export CXXFLAGS ; \
   FFLAGS="${FFLAGS:-%{build_fflags}}" ; export FFLAGS ; \

redhat-rpm-config.spec

@@ -6,7 +6,7 @@
 
 Summary: Red Hat specific rpm configuration files
 Name: redhat-rpm-config
-Version: 208
+Version: 209
 Release: 1%{?dist}
 # No version specified.
 License: GPL+
@@ -102,6 +102,7 @@ Requires: rpmautospec-rpm-macros
 Requires: fpc-srpm-macros
 Requires: gnat-srpm-macros
 Requires: nim-srpm-macros
+Requires: package-notes-srpm-macros
 %endif
 
 Requires: rpm >= 4.11.0
@@ -190,6 +191,9 @@ install -p -m 644 -t %{buildroot}%{_rpmluadir}/fedora/srpm forge.lua
 %doc buildflags.md
 
 %changelog
+* Thu Jan 13 2022 Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> - 209-1
+- Add package ELF note to the default LDFLAGS
+
 * Tue Jan 04 2022 Tom Stellard <tstellar@redhat.com> - 208-1
 - Call %%set_build_flags before %%build, %%check, and %%install stages