'spack buildcache list' should show all buildaches available. (#13002)

* binary cache: show all packages for compatible differing targets

* Don't restrict spack buildcache list to arch or os

* Fix from merge conflict

lib/spack/spack/binary_distribution.py

@@ -609,9 +609,6 @@ def get_specs(force=False):
         tty.warn("No Spack mirrors are currently configured")
         return {}
 
-    arch = spack.architecture.sys_type()
-    arch_spec = 'platform=%s os=%s target=:%s' % tuple(arch.split('-'))
-
     urls = set()
     for mirror_name, mirror_url in mirrors.items():
         if mirror_url.startswith('file'):
@@ -647,8 +644,7 @@ def get_specs(force=False):
                 # we need to mark this spec concrete on read-in.
                 spec = Spec.from_yaml(f)
                 spec._mark_concrete()
-                if spec.satisfies(arch_spec):
-                    _cached_specs.append(spec)
+                _cached_specs.append(spec)
 
     return _cached_specs