Ad-hoc Git commit versions: support submodules (#30037)

* Allow packages to add a 'submodules' property that determines when ad-hoc Git-commit-based versions should initialize submodules

* add support for ad-hoc git-commit-based versions to instantiate submodules if the associated package has a 'submodules' property and it indicates this should happen for the associated spec

* allow Package-level submodule request to influence all explicitly-defined version() in the Package

* skip test on windows which fails because of long paths

var/spack/repos/builtin.mock/packages/git-test/package.py

@@ -10,4 +10,6 @@ class GitTest(Package):
     """Mock package that uses git for fetching."""
     homepage = "http://www.git-fetch-example.com"
 
+    submodules = True
+
     version('git', git='to-be-filled-in-by-test')

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

@@ -50,6 +50,11 @@ class Axom(CachedCMakePackage, CudaPackage):
     version('0.3.0', tag='v0.3.0', submodules=True)
     version('0.2.9', tag='v0.2.9', submodules=True)
 
+    @property
+    def submodules(self):
+        # All git checkouts should also initialize submodules
+        return True
+
     patch('scr_examples_gtest.patch', when='@0.6.0:0.6.1')
 
     root_cmakelists_dir = 'src'