Use set_build_flags and -fno-semantic-interposition

see https://github.com/SELinuxProject/selinux/blob/master/README.md

CFLAGS that are encouraged to be set when overriding are:

  -fno-semantic-interposition for gcc or compilers that do not do this.

libsepol.spec

@@ -55,8 +55,9 @@ sed -i 's/fpic/fPIC/g' src/Makefile
 %endif
 
 %build
-make clean
-%make_build CFLAGS="%{optflags}" LDFLAGS="%{?__global_ldflags}"
+%set_build_flags
+CFLAGS="$CFLAGS -fno-semantic-interposition"
+%make_build
 
 %install
 mkdir -p ${RPM_BUILD_ROOT}/%{_lib} 
@@ -99,6 +100,7 @@ exit 0
 * Mon Jul 13 2020 Tom Stellard <tstellar@redhat.com> - 3.1-2
 - Use make macros
 - https://fedoraproject.org/wiki/Changes/UseMakeBuildInstallMacro
+- Use set_build_flags and -fno-semantic-interposition
 
 * Fri Jul 10 2020 Petr Lautrbach <plautrba@redhat.com> - 3.1-1
 - SELinux userspace 3.1 release