meson.build: Make keyutils independent from keyring

Commit 0db0fbb5cf ("Add conditional dependency for libkeyutils")
tried to provide a possibility for the user to disable keyutils
if not required by makeing it depend on the keyring feature. This
looked reasonable at a first glance (the unit test in tests/unit/
needs both), but the condition in meson.build fails if the feature
is meant to be detected automatically, and there is also another
spot in backends/meson.build where keyutils is used independently
from keyring. So let's remove the dependency on keyring again and
introduce a proper meson build option instead.

Cc: qemu-stable@nongnu.org
Fixes: 0db0fbb5cf ("Add conditional dependency for libkeyutils")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1842
Message-ID: <20230824094208.255279-1-thuth@redhat.com>
Reviewed-by: "Daniel P. Berrangé" <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/meson.build b/meson.build
index f426861..5139db2 100644
--- a/meson.build
+++ b/meson.build
@@ -1763,8 +1763,9 @@
                      method: 'pkg-config')
 endif
 keyutils = not_found
-if get_option('keyring').enabled()
-  keyutils = dependency('libkeyutils', required: false, method: 'pkg-config')
+if not get_option('libkeyutils').auto() or have_block
+  keyutils = dependency('libkeyutils', required: get_option('libkeyutils'),
+                        method: 'pkg-config')
 endif
 
 has_gettid = cc.has_function('gettid')
@@ -4229,6 +4230,7 @@
 summary_info += {'AF_ALG support':    have_afalg}
 summary_info += {'rng-none':          get_option('rng_none')}
 summary_info += {'Linux keyring':     have_keyring}
+summary_info += {'Linux keyutils':    keyutils}
 summary(summary_info, bool_yn: true, section: 'Crypto')
 
 # UI