Use bundled cppunit due to probable C++ ABI mismatch when linking with system cppunit, which is linked with another C++ ABI, and libc++

.abf.yml

@@ -28,3 +28,4 @@ sources:
   libreoffice-dictionaries-6.3.5.2.tar.xz: 15a2ad38276bb1c2249ffb8a8dfd9218c56e8a98
   libreoffice-help-6.3.5.2.tar.xz: 2cb7747b123c4bc8b0986889f55794a93e7b5319
   libreoffice-translations-6.3.5.2.tar.xz: 0ef79bb374a9919d8e49daedf6de4b39b81c3f27
+  cppunit-1.14.0.tar.gz: 3eba38567bad4e300f76c764f91a7301bacc716d

libreoffice.spec

@@ -48,6 +48,9 @@ Source1:	%{relurl}/%{ooname}-dictionaries-%{buildver}.tar.xz
 Source2:	%{relurl}/%{ooname}-help-%{buildver}.tar.xz
 Source3:	%{relurl}/%{ooname}-translations-%{buildver}.tar.xz
 Source4:	%{devexurl}/185d60944ea767075d27247c3162b3bc-unowinreg.dll
+%if %{with clang}
+Source5:	http://dev-www.libreoffice.org/src/cppunit-1.14.0.tar.gz
+%endif
 
 # Unused, should be dropped in future package updates
 Source10:	Mandriva-Rosa_Icons.tar.bz2
@@ -150,7 +153,9 @@ BuildRequires:	unixODBC-devel
 #BuildRequires:	vigra-devel
 BuildRequires:	gpgmepp-devel
 BuildRequires:	pkgconfig(bluez)
+%if !%{with clang}
 BuildRequires:	pkgconfig(cppunit) >= 1.14.0
+%endif
 BuildRequires:	pkgconfig(dbus-1)
 BuildRequires:	pkgconfig(expat)
 BuildRequires:	pkgconfig(libetonyek-0.1)
@@ -3016,6 +3021,9 @@ sed -i \
 	--with-external-thes-dir=%{_datadir}/dict/ooo \
 	--with-system-libs \
 	--with-system-ucpp \
+%if %{with clang}
+	--without-system-cppunit \
+%endif
 	--enable-ext-ct2n \
 	--enable-ext-numbertext \
 	--enable-ext-nlpsolver \