src: Stop hardcoding libc soname

ia64/alpha has SONAME "libc.so.6.1"

`None` works because Python is linked against libc, so the symbol is
already in our address space.

Fixes #21396

src/client/cockpit-client

@@ -47,11 +47,11 @@ except (ValueError, ImportError):
 
 libexecdir = os.path.realpath(__file__ + '/..')
 
-libc6 = ctypes.cdll.LoadLibrary('libc.so.6')
+sys_prctl = ctypes.CDLL(None).prctl
 
 
 def prctl(*args):
-    if libc6.prctl(*args) != 0:
+    if sys_prctl(*args) != 0:
         raise Exception('prctl() failed')
 
 

src/cockpit/transports.py

@@ -33,11 +33,11 @@
 
 from .jsonutil import JsonObject, get_int
 
-libc6 = ctypes.cdll.LoadLibrary('libc.so.6')
+sys_prctl = ctypes.CDLL(None).prctl
 
 
 def prctl(*args: int) -> None:
-    if libc6.prctl(*args) != 0:
+    if sys_prctl(*args) != 0:
         raise OSError('prctl() failed')