macOS: always set MACOSX_DEPLOYMENT_TARGET (#28797)

* core: Make platform environment an instance not class method

In preparation for accessing data constructed in __init__.

* macos: set consistent macosx deployment target

This should silence numerous warnings from mixed gcc/macos toolchains.

* perl: prevent too-new deployment target version

```
*** Unexpected MACOSX_DEPLOYMENT_TARGET=11
***
*** Please either set it to a valid macOS version number (e.g., 10.15) or to empty.
```

* Stylin'

* Add deployment target overrides to failing autoconf packages

* Move configure workaround to base autoconf package

This reverts commit 3c119eaf8b4fb37c943d503beacf5ad2aa513d4c.

* Stylin'

* macos: add utility functions for SDK

These aren't yet used but should probably be added to spack debug
report.

var/spack/repos/builtin/packages/perl/package.py

@@ -15,10 +15,10 @@
 import re
 from contextlib import contextmanager
 
-from llnl.util import tty
 from llnl.util.lang import match_predicate
 
 from spack import *
+from spack.operating_systems.mac_os import macos_version
 
 
 class Perl(Package):  # Perl doesn't use Autotools, it should subclass Package
@@ -297,24 +297,13 @@ def setup_dependent_package(self, module, dependent_spec):
     def setup_build_environment(self, env):
         spec = self.spec
 
-        # This is to avoid failures when using -mmacosx-version-min=11.1
-        # since not all Apple Clang compilers support that version range
-        # See https://eclecticlight.co/2020/07/21/big-sur-is-both-10-16-and-11-0-its-official/
-        # It seems that this is only necessary for older versions of the
-        # command line tools rather than the xcode/clang version.
-        if spec.satisfies('os=bigsur'):
-            pkgutil = Executable('pkgutil')
-            output = pkgutil('--pkg-info=com.apple.pkg.CLTools_Executables',
-                             output=str, error=str, fail_on_error=False)
-            match = re.search(r'version:\s*([0-9.]+)', output)
-            if not match:
-                tty.warn('Failed to detect macOS command line tools version: '
-                         + output)
-            else:
-                if Version(match.group(1)) < Version('12'):
-                    tty.warn("Setting SYSTEM_VERSION_COMPAT=1 due to older "
-                             "command line tools version")
-                    env.set('SYSTEM_VERSION_COMPAT', 1)
+        if (spec.version <= Version('5.34.0')
+            and spec.platform == 'darwin'
+            and macos_version() >= Version('10.16')):
+            # Older perl versions reject MACOSX_DEPLOYMENT_TARGET=11 or higher
+            # as "unexpected"; override the environment variable set by spack's
+            # platforms.darwin .
+            env.set('MACOSX_DEPLOYMENT_TARGET', '10.16')
 
         # This is how we tell perl the locations of bzip and zlib.
         env.set('BUILD_BZIP2', 0)

var/spack/repos/builtin/packages/py-scipy/package.py

@@ -3,9 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import platform
-
-
 class PyScipy(PythonPackage):
     """SciPy (pronounced "Sigh Pie") is a Scientific Library for Python.
     It provides many user-friendly and efficient numerical routines such
@@ -104,12 +101,6 @@ def setup_build_environment(self, env):
         if self.spec.satisfies('@:1.4 %gcc@10:'):
             env.set('FFLAGS', '-fallow-argument-mismatch')
 
-        # Kluge to get the gfortran linker to work correctly on Big
-        # Sur, at least until a gcc release > 10.2 is out with a fix.
-        # (There is a fix in their development tree.)
-        if platform.mac_ver()[0][0:2] == '11':
-            env.set('MACOSX_DEPLOYMENT_TARGET', '10.15')
-
     def install_options(self, spec, prefix):
         args = []
         if spec.satisfies('%fj'):

var/spack/repos/builtin/packages/python/package.py

@@ -6,7 +6,6 @@
 import glob
 import json
 import os
-import platform
 import re
 import sys
 
@@ -416,9 +415,6 @@ def setup_build_environment(self, env):
                       'errors may occur when installing Python modules w/ '
                       'mixed C/C++ source files.').format(self.version))
 
-        # Need this to allow python build to find the Python installation.
-        env.set('MACOSX_DEPLOYMENT_TARGET', platform.mac_ver()[0])
-
         env.unset('PYTHONPATH')
         env.unset('PYTHONHOME')