Fix suitesparse / cvxopt path configuration for Apple Silicon, Alpine Linux

[kcrisman]

I was able to successfully build Sage on M1 (see #30592) but had two main types of doctest errors.

> However, I did see some of this type as well in the sage/numerical tests: 
> 
> ImportError: dlopen(/Users/karl.crisman/Downloads/BrewSage/sage-9.4.beta0/local/lib/python3.9/site-packages/cvxopt/cholmod.cpython-39-darwin.so, 2): Symbol not found: _cholmod_l_allocate_dense 
> Referenced from: /Users/karl.crisman/Downloads/BrewSage/sage-9.4.beta0/local/lib/python3.9/site-packages/cvxopt/cholmod.cpython-39-darwin.so 
> Expected in: flat namespace 
> in /Users/karl.crisman/Downloads/BrewSage/sage-9.4.beta0/local/lib/python3.9/site-packages/cvxopt/cholmod.cpython-39-darwin.so 


otool -L /Users/karl.crisman/Downloads/BrewSage/sage-9.4.beta0/local/lib/python3.9/site-packages/cvxopt/cholmod.cpython-39-darwin.so 


/Users/karl.crisman/Downloads/BrewSage/sage-9.4.beta0/local/lib/python3.9/site-packages/cvxopt/cholmod.cpython-39-darwin.so:
	/opt/homebrew/opt/openblas/lib/libopenblas.0.dylib (compatibility version 0.0.0, current version 0.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1292.100.5) 

This apparently requires a change in the setup.py (see ​this sage-devel discussion):

if sys.platform.startswith("darwin"): 
SUITESPARSE_LIB_DIR = '/usr/local/lib' 
SUITESPARSE_INC_DIR = '/usr/local/include' 

to allow /opt/homebrew.

[kcrisman]

The following diff works and fixes the bad doctests for me (except some unrelated ones for graphics).

build/pkgs/cvxopt/patches/libsuitesparse_path.patch

@@ -1 +1 @@
 diff --git a/setup.py b/setup.py
-index d312416..4fa14c4 100644
 --- a/setup.py
 +++ b/setup.py
-@@ -58,9 +58,9 @@ if sys.platform.startswith("darwin"):
-     SUITESPARSE_LIB_DIR = '/usr/local/lib'
-     SUITESPARSE_INC_DIR = '/usr/local/include'
+@@ -56,11 +56,11 @@
+ if sys.platform.startswith("darwin"):
+     # macOS
+-    SUITESPARSE_LIB_DIR = '/usr/local/lib'
+-    SUITESPARSE_INC_DIR = '/usr/local/include'
++    SUITESPARSE_LIB_DIR = '/opt/homebrew/lib'
++    SUITESPARSE_INC_DIR = '/opt/homebrew/include'
  else:
 -    if glob("/usr/lib/x86_64-linux-gnu/libsuitesparse*"):
 -        # Ubuntu/Debian

I am not currently in a position to make a proper branch with this testing setup, my apologies, and in any case it needs some additional logic to test for which version of MacOS we have and/or if homebrew is being used.

[mkoeppe]

Upstream report...

[kcrisman]

Upstream report...

Will they see this as a bug? I already asked about whether to report upstream ​here.

[kcrisman]

​https://github.com/cvxopt/cvxopt/issues/195

[mkoeppe]

These defaults in cvxopt's setup.py can be overridden using environment variables CVXOPT_SUITESPARSE_INC_DIR, CVXOPT_SUITESPARSE_LIB_DIR. We already set these variables when we build our own suitesparse (then SAGE_SUITESPARSE_PREFIX is nonempty).

On macOS, we could just set these variables also (to something arbitrary) when system suitesparse is in use.

See also ​https://trac.sagemath.org/ticket/33083#comment:40 - a related issue on alpine.