compilers: add .stdcxx_libs to the compiler adaptor (#49873)

This property is used by a few recipes, including `cp2k` under
certain configurations

Signed-off-by: Massimiliano Culpo <massimiliano.culpo@gmail.com>

lib/spack/spack/compilers/adaptor.py

@@ -190,6 +190,10 @@ def f77(self):
         self._lang_exists_or_raise("f77", lang=Languages.FORTRAN)
         return self.compilers[Languages.FORTRAN].package.fortran
 
+    @property
+    def stdcxx_libs(self):
+        return self._maybe_return_attribute("stdcxx_libs", lang=Languages.CXX)
+
 
 class DeprecatedCompiler(lang.DeprecatedProperty):
     def __init__(self) -> None:

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

@@ -138,6 +138,7 @@ def cfg_files(self):
     }
 
     implicit_rpath_libs = ["libclang"]
+    stdcxx_libs = ("-lstdc++",)
 
     def _standard_flag(self, *, language: str, standard: str) -> str:
         flags = {

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

@@ -618,7 +618,7 @@ def supported_languages(self):
     opt_flags = ["-O", "-O0", "-O1", "-O2", "-O3", "-Os", "-Ofast", "-Og"]
 
     implicit_rpath_libs = ["libgcc", "libgfortran"]
-    stdcxx_libs = "-lstdc++"
+    stdcxx_libs = ("-lstdc++",)
 
     def _standard_flag(self, *, language, standard):
         flags = {

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

@@ -28,6 +28,8 @@ class Grackle(Package):
     depends_on("libtool", when="@2.2:")
 
     depends_on("c", type="build")
+    depends_on("cxx", type="build")
+
     depends_on("fortran", type="build")
     depends_on("tcsh", type="build")
     depends_on("mpi")