Turns out that changing the ltrace.spec %build script to:
%build
./autogen.sh
export CFLAGS="%{optflags} -Wall -Wno-unused-local-typedefs -DNDEBUG
-Wno-error"
%configure --disable-shared
%make_build
results in a rpmbuild with assertions disabled. A ltrace binary produced this
way no longer fails with the test c++ binaries with debug info enabled.