gcc-runtime: add separate package for gcc runtime libs

The gcc-runtime package adds a separate node for gcc's dynamic runtime
libraries.

This should help with:

1. binary caches where rpaths for compiler support libs cannot be
   relocated because the compiler is missing on the target system
2. creating "minimal" container images

The package is versioned like `gcc` (in principle it could be
unversioned, but Spack doesn't always guarantee not mixing compilers)

lib/spack/spack/main.py

@@ -36,6 +36,7 @@
 import spack.config
 import spack.environment as ev
 import spack.modules
+import spack.package_base
 import spack.paths
 import spack.platforms
 import spack.repo
@@ -607,6 +608,7 @@ def setup_main_options(args):
             [(key, [spack.paths.mock_packages_path])]
         )
         spack.repo.PATH = spack.repo.create(spack.config.CONFIG)
+        spack.package_base.WITH_GCC_RUNTIME = False
 
     # If the user asked for it, don't check ssl certs.
     if args.insecure:

lib/spack/spack/package_base.py

@@ -53,6 +53,7 @@
 import spack.util.environment
 import spack.util.path
 import spack.util.web
+from spack.directives import _depends_on
 from spack.filesystem_view import YamlFilesystemView
 from spack.install_test import (
     PackageTest,
@@ -76,6 +77,7 @@
 """Allowed URL schemes for spack packages."""
 _ALLOWED_URL_SCHEMES = ["http", "https", "ftp", "file", "git"]
 
+WITH_GCC_RUNTIME = True
 
 #: Filename for the Spack build/install log.
 _spack_build_logfile = "spack-build-out.txt"
@@ -371,6 +373,20 @@ def _wrapper(instance, *args, **kwargs):
     return _execute_under_condition
 
 
+class BinaryPackage:
+    """This adds a universal dependency on gcc-runtime."""
+
+    def maybe_depend_on_gcc_runtime(self):
+        # Do not depend on itself, and allow tests to disable this universal dep
+        if self.name == "gcc-runtime" or not WITH_GCC_RUNTIME:
+            return
+        for v in ["13", "12", "11", "10", "9", "8", "7", "6", "5", "4"]:
+            _depends_on(self, f"gcc-runtime@{v}:", type="link", when=f"%gcc@{v} platform=linux")
+            _depends_on(self, f"gcc-runtime@{v}:", type="link", when=f"%gcc@{v} platform=cray")
+
+    _directives_to_be_executed = [maybe_depend_on_gcc_runtime]
+
+
 class PackageViewMixin:
     """This collects all functionality related to adding installed Spack
     package to views. Packages can customize how they are added to views by
@@ -433,7 +449,7 @@ def remove_files_from_view(self, view, merge_map):
 Pb = TypeVar("Pb", bound="PackageBase")
 
 
-class PackageBase(WindowsRPath, PackageViewMixin, metaclass=PackageMeta):
+class PackageBase(WindowsRPath, PackageViewMixin, BinaryPackage, metaclass=PackageMeta):
     """This is the superclass for all spack packages.
 
     ***The Package class***

lib/spack/spack/test/conftest.py

@@ -57,6 +57,11 @@
 from spack.util.pattern import Bunch
 
 
+@pytest.fixture(scope="session", autouse=True)
+def drop_gcc_runtime():
+    spack.package_base.WITH_GCC_RUNTIME = False
+
+
 def ensure_configuration_fixture_run_before(request):
     """Ensure that fixture mutating the configuration run before the one where
     the function is called.