Fix building PyTorch when using setup.py as the build command

When changing `use_pip` after `PythonPackage.__init__` called
`determine_install_command` the change is not honored.
Call it again after the change.

This also requires to make it idempotent so all member variables changed
in that function need to be set in all cases.

Fixes #3570

Author: Flamefire

easybuild/easyblocks/generic/pythonpackage.py

@@ -474,7 +474,6 @@ def __init__(self, *args, **kwargs):
         self.pylibdir = UNKNOWN
         self.all_pylibdirs = [UNKNOWN]
 
-        self.py_installopts = []
         self.install_cmd_output = ''
 
         # make sure there's no site.cfg in $HOME, because setup.py will find it and use it
@@ -499,8 +498,6 @@ def __init__(self, *args, **kwargs):
         # figure out whether this Python package is being installed for multiple Python versions
         self.multi_python = 'Python' in self.cfg['multi_deps']
 
-        # determine install command
-        self.use_setup_py = False
         self.determine_install_command()
 
         # avoid that pip (ab)uses $HOME/.cache/pip
@@ -517,7 +514,9 @@ def determine_install_command(self):
         """
         Determine install command to use.
         """
+        self.py_installopts = []
         if self.cfg.get('use_pip', True) or self.cfg.get('use_pip_editable', False):
+            self.use_setup_py = False
             self.install_cmd = PIP_INSTALL_CMD
 
             pip_verbose = self.cfg.get('pip_verbose', None)
@@ -546,8 +545,8 @@ def determine_install_command(self):
         else:
             self.use_setup_py = True
             self.install_cmd = SETUP_PY_INSTALL_CMD
-            install_target = self.cfg.get_ref('install_target')
 
+            install_target = self.cfg.get_ref('install_target')
             if install_target == EASY_INSTALL_TARGET:
                 self.install_cmd += " %(loc)s"
                 self.py_installopts.append('--no-deps')

easybuild/easyblocks/p/pytorch.py

@@ -240,6 +240,7 @@ def __init__(self, *args, **kwargs):
         if self.cfg['use_pip'] is None and pytorch_version >= '2.0':
             self.log.info("Auto-enabling use of pip to install PyTorch >= 2.0, since 'use_pip' is not set")
             self.cfg['use_pip'] = True
+            self.determine_install_command()
 
     def fetch_step(self, skip_checksums=False):
         """Fetch sources for installing PyTorch, including those for tests."""