Force C++14 as this code is not C++17 ready

fldigi.spec

@@ -1,6 +1,6 @@
 Name:           fldigi
 Version:        4.1.13
-Release:        3%{?dist}
+Release:        4%{?dist}
 Summary:        Digital modem program for Linux
 
 License:        GPLv3+  
@@ -61,6 +61,7 @@ PDF User Manual for %{name} and flarq.
 
 
 %build
+export CXXFLAGS="-std=c++14 $RPM_OPT_FLAGS"
 %if 0%{?rhel} && 0%{?rhel} < 8
 %configure --enable-static
 %else
@@ -114,6 +115,9 @@ appstream-util validate-relax --nonet %{buildroot}%{_datadir}/appdata/*.appdata.
 
 
 %changelog
+* Tue Aug 18 2020 Jeff Law <law@redhat.com> - 4.1.13-4
+- Force C++14 as this code is not C++17 ready
+
 * Mon Jul 27 2020 Fedora Release Engineering <releng@fedoraproject.org> - 4.1.13-3
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_33_Mass_Rebuild