[Bug-gsl] work around silly /bin/sh on Solaris

[Martin Jansche]

Hi Brian,

I've run into a problem when compiling GSL on Solaris (tested with
SunOS-5.8), which can ultimately be traced back to the fact that the
built-in "test" command of /bin/sh on Solaris does not support a
simple test for existence of a file (this is discussed further in the
documentation for Autoconf).  The only affected file is
gsl/Makefile.am.  There's a one-character fix (see patch below):
change "-e" to "-r".

-- mj

Index: gsl/Makefile.am
===================================================================
RCS file: /cvs/gsl/gsl/gsl/Makefile.am,v
retrieving revision 1.4
diff -r1.4 Makefile.am
6c6
<         test -e $$BASENAME || $(LN_S) $$h $$BASENAME; \
---
>         test -r $$BASENAME || $(LN_S) $$h $$BASENAME; \