Installation of third-party SUBDIRS

[Matwey V. Kornilov]

Hi,

I use a couple of third-party libraries in my software. I use SUBDIRS 
variable in my Makefile.am and AC_CONFIG_SUBDIRS in my configure.in. How to 
suppress installation of SUBDIRed projects? I just use they for static 
linkage with my binary and don't need third-party headers and libraries 
installed.