unix-ffi/ffilib/ffilib.py: Extend libc versions range.

This commit extends the range of libc library versions that are looked
up when required by user code.

FreeBSD 14.1-RELEASE and later versions require an update to the range
since they bumped up their libc major version, from 6 to 7.  This has
the side-effect of guaranteeing at least one failed lookup on modern
Linux systems, where the libc is still at version 6.

With updated FreeBSD support in MicroPython core, now `sys.platform`
properly returns `freebsd`.  This required a minor change in the code
deciding whether to look for `.so`, `.dylib`, or `.dll` files, since
`linux` is no longer the default fallback for generic unix systems.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

Author: agatti

unix-ffi/ffilib/ffilib.py

@@ -17,7 +17,7 @@ def open(name, maxver=10, extra=()):
         pass
 
     def libs():
-        if sys.platform == "linux":
+        if sys.platform in ("linux", "freebsd"):
             yield "%s.so" % name
             for i in range(maxver, -1, -1):
                 yield "%s.so.%u" % (name, i)
@@ -39,7 +39,7 @@ def libs():
 
 
 def libc():
-    return open("libc", 6)
+    return open("libc", 7)
 
 
 # Find out bitness of the platform, even if long ints are not supported