meson.build: fix libgcrypt detection on system without libgcrypt-config

libgcrypt starts providing correct pkg-config configuration since 1.9,
in parallel with libgcrypt-config. Since 1.11 it may also stop
installing libgcrypt-config in some scenarios. Use the auto method for
detection of libgcrypt, in which meson will try both pkg-config and
libgcrypt-config.

Auto method for libgcrypt is supported by meson since 0.49.0, which is
higher than the version qemu requires.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
diff --git a/meson.build b/meson.build
index 4eca361..ec6fb7d 100644
--- a/meson.build
+++ b/meson.build
@@ -1696,7 +1696,6 @@
 if not gnutls_crypto.found()
   if (not get_option('gcrypt').auto() or have_system) and not get_option('nettle').enabled()
     gcrypt = dependency('libgcrypt', version: '>=1.8',
-                        method: 'config-tool',
                         required: get_option('gcrypt'))
     # Debian has removed -lgpg-error from libgcrypt-config
     # as it "spreads unnecessary dependencies" which in