Fix ABI regression in tbb::empty_task caused by switch to LTO

Resolves: rhbz#1939012

tbb.spec

@@ -1,7 +1,7 @@
 Name:    tbb
 Summary: The Threading Building Blocks library abstracts low-level threading details
 Version: 2020.3
-Release: 6%{?dist}
+Release: 7%{?dist}
 License: ASL 2.0
 URL:     http://threadingbuildingblocks.org/
 
@@ -27,6 +27,10 @@ Patch2: tbb-2019-test-thread-monitor.patch
 # than 2 threads will be available to use it.
 Patch3: tbb-2019-test-task-scheduler-init.patch
 
+# Fix ABI break resulting from tbb::empty_task being removed from libtbb.so's
+# exported symbols
+Patch4: tbb-mark-empty_task-execute-with-gnu-used.patch
+
 BuildRequires: cmake
 BuildRequires: doxygen
 BuildRequires: gcc-c++
@@ -201,6 +205,9 @@ cmake \
 %{python3_sitearch}/__pycache__/TBB*
 
 %changelog
+* Thu Jun  3 2021 Thomas Rodgers <trodgers@redhat.com> - 2020.3-6
+- Fix ABI regression in tbb::empty_task caused by switch to LTO
+
 * Fri Apr 16 2021 Mohan Boddu <mboddu@redhat.com> - 2020.3-6
 - Rebuilt for RHEL 9 BETA on Apr 15th 2021. Related: rhbz#1947937