fix build where %%qmake_qt5 isn't available (yet)

qwt.spec

@@ -94,7 +94,7 @@ Requires: %{name}-qt5%{?_isa} = %{version}-%{release}
 %if 0%{?qt5}
 mkdir %{_target_platform}-qt5
 pushd %{_target_platform}-qt5
-%{qmake_qt5} QWT_CONFIG+=QwtPkgConfig ..
+%{?qmake_qt5}%{?!qmake_qt5:%{_qt5_qmake}} QWT_CONFIG+=QwtPkgConfig ..
 
 make %{?_smp_mflags}
 popd
@@ -184,7 +184,6 @@ cp -alf %{buildroot}%{_qt4_docdir}/html/qwt/ \
 %endif
 
 
-
 %changelog
 * Mon Dec 01 2014 Rex Dieter <rdieter@fedoraproject.org> - 6.1.1-3
 - %%build: use %%qmake-qt? macro variant