Variable S4_LIBNAME not set in Makefile.common

[kwrobert]

When attempting to compile the Python extensions on Ubuntu 16.04 using the following command:

make S4_pyext

The following error occurs:

x86_64-linux-gnu-gcc: error: No such file or directory

Thiserror message is misleading. x86_64-linux-gnu-gcc exists and is upset because its being supplied the variable $S4_LIBNAME, which is empty. Not sure what this variable is supposed to be set to, but setting it to the proper value should fix things.

[kwrobert]

Looking at older commits, I think its supposed to be S4_LIBNAME=$(OBJDIR)/libS4.a

You can add this at the top of Makefile.common and everything compiles as it should.