Fix openblas to build with Xcode 12

[jhpalmieri]

OpenBLAS fails to build with Xcode 12 (as can be seen for example in https://github.com/mkoeppe/sage/runs/1141519170). The fix at OpenMathLib/OpenBLAS#2805, more precisely,
OpenMathLib/OpenBLAS#2808 - and can be backported to 0.3.9 or 0.3.10.

This is marked critical, not a blocker, since there is a workable homebrew package that can be used instead.

Upstream: None of the above - read trac for reasoning.

CC: @mkoeppe @jhpalmieri

Component: packages: standard

Author: Dima Pasechnik

Branch/Commit: b4315c2

Reviewer: John Palmieri

Issue created by migration from https://trac.sagemath.org/ticket/30610

[mkoeppe]

Description changed:

--- 
+++ 
@@ -1,3 +1,3 @@
-OpenBLAS fails to build with Xcode 12. Partial fix at https://github.com/xianyi/OpenBLAS/issues/2805, but this does not appear to completely solve the problem.
+OpenBLAS fails to build with Xcode 12 (as can be seen for example in https://github.com/mkoeppe/sage/runs/1141519170). Partial fix at https://github.com/xianyi/OpenBLAS/issues/2805, but this does not appear to completely solve the problem.
 
 This is marked critical, not a blocker, since there is a workable homebrew package that can be used instead.

[dimpase]

Description changed:

--- 
+++ 
@@ -1,3 +1,4 @@
-OpenBLAS fails to build with Xcode 12 (as can be seen for example in https://github.com/mkoeppe/sage/runs/1141519170). Partial fix at https://github.com/xianyi/OpenBLAS/issues/2805, but this does not appear to completely solve the problem.
+OpenBLAS fails to build with Xcode 12 (as can be seen for example in https://github.com/mkoeppe/sage/runs/1141519170). The fix at https://github.com/xianyi/OpenBLAS/issues/2805, more precisely, 
+https://github.com/xianyi/OpenBLAS/pull/2808 - and can be backported to 0.3.9 or 0.3.10.
 
 This is marked critical, not a blocker, since there is a workable homebrew package that can be used instead.

[dimpase]

comment:3

see
OpenMathLib/OpenBLAS#2805 (comment)

applying a patch to OpenBLAS's lapack.h allows one to build version 0.3.9

[dimpase]

Commit: b4315c2

[dimpase]

Branch: u/dimpase/packages/openblas/xcode12patch

[dimpase]

Upstream: None of the above - read trac for reasoning.

[dimpase]

New commits:

b4315c2

backport of the relevant part of upstream PR 2808

[dimpase]

Author: Dima Pasechnik

[jhpalmieri]

comment:6

This works for me.

[jhpalmieri]

Reviewer: John Palmieri