Fix Fedora build flags injection

- Resolves #1548832

Signed-off-by: Rafael Santos <rdossant@redhat.com>

libtommath.spec

@@ -1,6 +1,6 @@
 Name:           libtommath
 Version:        1.0.1
-Release:        4%{?dist}
+Release:        5%{?dist}
 Summary:        A portable number theoretic multiple-precision integer library
 License:        Public Domain
 URL:            http://www.libtom.net/
@@ -53,11 +53,12 @@ sed -i \
     %{name}.pc.in
 
 %build
-%make_build V=1 CFLAGS="%{optflags} -I./" -f makefile.shared
+%set_build_flags
+%make_build V=1 CFLAGS="$CFLAGS -I./" -f makefile.shared
 %make_build V=1 -f makefile poster manual docs
 
 %install
-%make_install V=1 CFLAGS="%{optflags} -I./" PREFIX=%{_prefix} LIBPATH=%{_libdir} -f makefile.shared
+%make_install V=1 CFLAGS="$CFLAGS -I./" PREFIX=%{_prefix} LIBPATH=%{_libdir} -f makefile.shared
 
 find %{buildroot} -name '*.la' -delete
 find %{buildroot} -name '*.a' -delete
@@ -77,6 +78,9 @@ find %{buildroot} -name '*.a' -delete
 %doc doc/bn.pdf doc/poster.pdf doc/tommath.pdf
 
 %changelog
+* Thu Apr 05 2018 Rafael Santos <rdossant@redhat.com> - 1.0.1-5
+- Resolves #1548832 - Fix Fedora build flags injection
+
 * Sun Feb 25 2018 Florian Weimer <fweimer@redhat.com> - 1.0.1-4
 - Add BuildRequires: ghostscript-tools-dvipdf