[android] Improve CFKnownLocations.

The usage of CFKnownLocations from Swift Foundation seems to be reduced
to both _kCFKnownLocationUserAny and _kCFKnownLocationUserCurrent. From
the public API of Swift Foundation there's no way to get to
_kCFKnownLocationUserByName. Supporting UserAny is, therefore,
necessary.

There are some ways of accessing _kCFKnownLocationUserByName from the CF
API, but it seems that the API only allows Current or Any, even if they
are not enforced. In any case, Android do not have Unix usernames, so
ByName doesn't make sense, and should be always the same as UserCurrent.

The change in code makes every code path fall back to the current user
(which should be also any user, and any user by name, because the
platforms limitations).

Additionally, instead of picking up a CFFIXEDUSE_HOME, request the home
directory from CFUtilities, since it deals with HOME, HOMEDIR and
CFFIXED_HOME appropiedly, since HOME is necessary for many other things.

The current code will have aborted the test suite, while the modified
code, passes the test suite for UserDefaults.

Author: drodriguez

CoreFoundation/Base.subproj/CFKnownLocations.c

@@ -12,6 +12,7 @@
 #include <CoreFoundation/CFString.h>
 #include "CFPriv.h"
 #include "CFInternal.h"
+#include "CFUtilities.h"
 
 #include <assert.h>
 
@@ -94,21 +95,15 @@ CFURLRef _Nullable _CFKnownLocationCreatePreferencesURLForUser(CFKnownLocationUs
 #elif TARGET_OS_ANDROID
 
     switch (user) {
-    case _kCFKnownLocationUserAny:
-    case _kCFKnownLocationUserByName:
-      abort();
-    case _kCFKnownLocationUserCurrent: {
-      const char *buffer = getenv("CFFIXED_USER_HOME");
-      if (buffer == NULL || *buffer == '\0') {
-        CFLog(__kCFLogAssertion, CFSTR("CFFIXED_USER_HOME is unset"));
-        HALT;
-      }
-
-      CFURLRef userdir = CFURLCreateFromFileSystemRepresentation(kCFAllocatorSystemDefault, (const unsigned char *)buffer, strlen(buffer), true);
-      location = CFURLCreateWithFileSystemPathRelativeToBase(kCFAllocatorSystemDefault, CFSTR("/Apple/Library/Preferences"), kCFURLPOSIXPathStyle, true, userdir);
-      CFRelease(userdir);
-      break;
-    }
+        case _kCFKnownLocationUserAny:
+        case _kCFKnownLocationUserByName:
+            // fallthrough
+        case _kCFKnownLocationUserCurrent: {
+            CFURLRef userdir = CFCopyHomeDirectoryURL();
+            location = CFURLCreateWithFileSystemPathRelativeToBase(kCFAllocatorSystemDefault, CFSTR("/Library/Preferences"), kCFURLPOSIXPathStyle, true, userdir);
+            CFRelease(userdir);
+            break;
+        }
     }
 
 #else