Alien::GSL should not install GSL first to build directory and then copy the install to the dist directory: gsl-config --prefix gives wrong path

[hakonhagland]

I noticed in issue #220 that Build (and Build.PL) is getting the wrong path for the prefix to GSL via the command gsl-config --prefix. For example the output for Build when trying to build Math::GSL on Windows 10 with MSYS2 starts with:

$ ./Build
Building Math-GSL
Processing 2.6 XS files, GSL 2.6 (via gsl-config) at /home/hakon/.cpanm/work/1595801186.15197/Alien-GSL-1.02/blib/lib/auto/share/dist/Alien-GSL
Compiler        = gcc (GCC) 9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[...]

Notice the line:

GSL 2.6 (via gsl-config) at /home/hakon/.cpanm/work/1595801186.15197/Alien-GSL-1.02/blib/lib/auto/share/dist/Alien-GSL

It is using the cpanm work directory /home/hakon/.cpanm instead of the the dist install directory
/usr/share/perl5/site_perl/auto/share/dist/Alien-GSL. This is obviously a problem if cpanm cleans up the work directory (which it does from time to time).

I believe this is mainly an issue of Alien::GSL and will report it at their issue tracker too. It has also been reported in #169, and at the Alien::GSL issue tracker, see this issue and it looks like their pull request no 7 will fix the issue.