libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I./Config -O3 -march=native -ffast-math -funroll-loops -I/shared/apps/cln/cln-1.3.4/INSTALL/include -I/shared/apps/ginac/ginac-1.5.6/usr/include -I./src -O2 -Wall -MT src/lowe.lo -MD -MP -MF src/.deps/lowe.Tpo -c src/lowe.cpp  -fPIC -DPIC -o src/lowe.o
In file included from /shared/apps/cln/cln-1.3.4/INSTALL/include/cln/string.h:9:0,
                 from /shared/apps/gnu-compilers/gnu-4.8.1/gcc-4.8.1/INSTALL/include/c++/4.8.1/cstring:42

^ in the above, you can see that -I goes for /shared/apps/cln/cln-1.3.4/INSTALL/include, but <cstring> is trying to include /shared/apps/cln/cln-1.3.4/INSTALL/include/cln/string.h which should be included as <cln/string.h>