fix R on macOS xcode 12

[dimpase]

configure fails to find bzlib, as the test function misses #includes
This is fixed upstream in the trunk (in Sept. 2020).

Upstream: Fixed upstream, but not in a stable release.

CC: @mkoeppe @jhpalmieri @slel

Component: packages: standard

Author: Dima Pasechnik

Branch/Commit: 376af90

Reviewer: John Palmieri

Issue created by migration from https://trac.sagemath.org/ticket/30631

[dimpase]

Commit: 376af90

[dimpase]

Branch: u/dimpase/build/homebrewbzip

[dimpase]

New commits:

376af90

backport configure fix from trunk, add bzip2 paths

[dimpase]

Author: Dima Pasechnik

[jhpalmieri]

comment:3

This builds for me with Xcode 12. For what it's worth, the changes to .homebrew-build-env didn't have any effect for me since I don't have bzip2 installed via homebrew. Just using the system version seems to work fine.

[dimpase]

comment:4

OK, so then these changes to .homebrew-build-env are not needed in fact. I added them as I tried to get R to recognise bzip2, so I thought it might be a problem here.

[dimpase]

comment:5

On the other hand there is no harm in the modification of .homebrew-build-env - it merely make sure that if Homebrew's bzip2 is installed then it gets used.

[jhpalmieri]

comment:6

Sounds good.

[jhpalmieri]

Reviewer: John Palmieri

[slel]

comment:7

Marking as critical since it is needed for Xcode 12 support.

[vbraun]

Changed branch from u/dimpase/build/homebrewbzip to 376af90