Windows: fix MSVC version handling (#37711)

MSVC compiler logic was using string parsing to extract version
from compiler spec, which was fragile. This broke in #37572, so has
been fixed and made more robust by using attribute access.

lib/spack/spack/compilers/msvc.py

@@ -30,7 +30,7 @@
 
 
 def get_valid_fortran_pth(comp_ver):
-    cl_ver = str(comp_ver).split("@")[1]
+    cl_ver = str(comp_ver)
     sort_fn = lambda fc_ver: StrictVersion(fc_ver)
     sort_fc_ver = sorted(list(avail_fc_version), key=sort_fn)
     for ver in sort_fc_ver:
@@ -75,7 +75,7 @@ class Msvc(Compiler):
     # file based on compiler executable path.
 
     def __init__(self, *args, **kwargs):
-        new_pth = [pth if pth else get_valid_fortran_pth(args[0]) for pth in args[3]]
+        new_pth = [pth if pth else get_valid_fortran_pth(args[0].version) for pth in args[3]]
         args[3][:] = new_pth
         super(Msvc, self).__init__(*args, **kwargs)
         if os.getenv("ONEAPI_ROOT"):