Introduce --module-cache-suffix to allow multiple caches

This is useful when having multiple module trees (i.e. different `--installprefix`)
to not overwrite the cache file of one with the other when using `--update-modules-tool-cache`.
Inspired by how LMod itself creates the cache, e.g.
`~/.cache/lmod/spiderT.rapids_x86_64_Linux.lua`

easybuild/tools/config.py

@@ -239,6 +239,7 @@ def mk_full_default_path(name, prefix=DEFAULT_PREFIX):
         'job_polling_interval',
         'job_target_resource',
         'locks_dir',
+        'module_cache_suffix',
         'modules_footer',
         'modules_header',
         'mpi_cmd_template',

easybuild/tools/modules.py

@@ -1436,7 +1436,8 @@ def update(self):
                 # don't actually update local cache when testing, just return the cache contents
                 return stdout
             else:
-                cache_fp = os.path.join(self.USER_CACHE_DIR, 'moduleT.lua')
+                suffix = build_option('module_cache_suffix') or ''
+                cache_fp = os.path.join(self.USER_CACHE_DIR, 'moduleT%s.lua' % suffix)
                 self.log.debug("Updating Lmod spider cache %s with output from '%s'" % (cache_fp, ' '.join(cmd)))
                 cache_dir = os.path.dirname(cache_fp)
                 if not os.path.exists(cache_dir):

easybuild/tools/options.py

@@ -461,6 +461,9 @@ def override_options(self):
                                   "environment variable and its value separated by a colon (':')",
                                   None, 'store', DEFAULT_MINIMAL_BUILD_ENV),
             'minimal-toolchains': ("Use minimal toolchain when resolving dependencies", None, 'store_true', False),
+            'module-cache-suffix': ("Suffix to add to the cache file name (before the extension) "
+                                    "when updating the modules tool cache",
+                                    None, 'store', None),
             'module-only': ("Only generate module file(s); skip all steps except for %s" % ', '.join(MODULE_ONLY_STEPS),
                             None, 'store_true', False),
             'modules-tool-version-check': ("Check version of modules tool being used", None, 'store_true', True),