rewrite embedded paths at install time

[reidpr]

Closes #683.

This PR changes library paths in sh and Python code to be valid in the source directory and removes the lib/charliecloud symlink. It then re-writes these paths to be valid for the install location at install time.

[reidpr]

@ana @olifre @lnussbaum @wiene : I'd love opinions on how distributions feel about this approach.

[olifre]

Since the critical part for distros is valid for the install location at install time, I don't see any problem with this approach. To confirm this, I also tried to run this branch through Gentoo's packaging and the package manager was happy (i.e. not automated flagging), so that seems good for Gentoo 👍 .

[lucaudill]

LGTM

[wiene]

At present the situation for Debian is the following:
A Debian specific patch is applied to modify the path to the tests in ch-test (CHTEST_DIR).

I glanced through the changes. Unless I overlooked something, it seems that a patch is still needed after the modifications of PR have been applied. Removing the above mentioned patch and applying this PR, I get

CHTEST_DIR=/usr/libexec/installed-tests/charliecloud/test

in ch-test. This is closer than before, but not precisely what I am looking for:

CHTEST_DIR=/usr/libexec/installed-tests/charliecloud

Of course, it is nice to get rid of distribution specific patches. On the other hand, if this only affects Debian, it is also fine to keep the patch.

[e4t]

@ana @olifre @lnussbaum @wiene : I'd love opinions on how distributions feel about this approach.

@ana asked me to respond for her:
SUSE/openSUSE uses libexec on the rolling release (openSUSE Tumbleweed) and any upcoming product (ALP etc), however, SLE and Leap still adhere to the somewhat older FHS 2.3 standard.
For this RPM-based Linux distros provide a set of RPM predefined macros (%_libexecdir) which are set to the path elements of the underlying system. These will be specified during configure (using a predefined %_configure macro for convenience). Thus, allowing these paths / path elements to be configurable allows distributions to set them to their needs without extensive patching.

[reidpr]

Thanks folks.

@wiene I believe the latest version of this PR will let you eliminate your patch.

[lucaudill]

LGTM

[wiene]

@wiene I believe the latest version of this PR will let you eliminate your patch.

I can confirm that the patch can be removed thanks to this PR. Many thanks!