spkg-configure.m4 for pkgconf

[dimpase]

pkgconf is an implementation of widely used pkg-config.
In fact, pkg-config can be configured to look at certain directories, so we can use the one on the system.

This is what the branch does - it check for pkg-config presense,
and if it is there is sets up/updates the env.var. PKG_CONFIG_PATH
in src/bin/sage-env-config. As pkg-config looks in dirs in PKG_CONFIG_PATH first, anything that Sage installs there overrides the system ones.

CC: @embray @kiwifb @isuruf @antonio-rojas

Component: build: configure

Author: Dima Pasechnik

Branch/Commit: ed84fa2

Reviewer: Isuru Fernando

Issue created by migration from https://trac.sagemath.org/ticket/27827

[embray]

comment:1

As the Sage-8.8 release milestone is pending, we should delete the sage-8.8 milestone for tickets that are not actively being worked on or that still require significant work to move forward. If you feel that this ticket should be included in the next Sage release at the soonest please set its milestone to the next release milestone (sage-8.9).

[dimpase]

comment:2

the plan is to install PKG_CONFIG_PATH=SAGE_LOCAL/lib/pkgconfig into src/bin/sage-env-config in case the system has pkg-config installed.

[dimpase]

New commits:

f77b4c1

spkg-configure.m4 for pkgconf

[dimpase]

Author: Dima Pasechnik

[dimpase]

Branch: u/dimpase/packages/pkgconf

[dimpase]

Commit: f77b4c1

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

836f5ba

spkg-configure.m4 for pkgconf

[sagetrac-git]

Changed commit from f77b4c1 to 836f5ba

[dimpase]

Description changed:

--- 
+++ 
@@ -1,4 +1,6 @@
 pkgconf is an implementation of widely used pkg-config.
-In fact, pkg-config can be configured to look at certain directories, so we can use the one on the system, I suppose. 
+In fact, pkg-config can be configured to look at certain directories, so we can use the one on the system.
 
-Fiddly, but probably doable
+This is what the branch does - it check for `pkg-config` presense,
+and if it is there is sets up/updates the env.var. `PKG_CONFIG_PATH`
+in `src/bin/sage-env-config`. As `pkg-config` looks in dirs in `PKG_CONFIG_PATH` first, anything that Sage installs there overrides the system ones.