meson: update unsupported host/CPU messages

Unsupported CPU and OSes are not really going away, but the
project simply does not guarantee that they work.  Rephrase
the messages accordingly.  While at it, move the warning for
TCI performance at the end where it is more visible.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

meson.build

@@ -678,9 +678,7 @@ endif
 tcg_arch = host_arch
 if get_option('tcg').allowed()
   if host_arch == 'unknown'
-    if get_option('tcg_interpreter')
-      warning('Unsupported CPU @0@, will use TCG with TCI (slow)'.format(cpu))
-    else
+    if not get_option('tcg_interpreter')
       error('Unsupported CPU @0@, try --enable-tcg-interpreter'.format(cpu))
     endif
   elif get_option('tcg_interpreter')
@@ -4317,28 +4315,37 @@ summary_info += {'selinux':           selinux}
 summary_info += {'libdw':             libdw}
 summary(summary_info, bool_yn: true, section: 'Dependencies')
 
-if not supported_cpus.contains(cpu)
+if host_arch == 'unknown'
   message()
-  warning('SUPPORT FOR THIS HOST CPU WILL GO AWAY IN FUTURE RELEASES!')
+  warning('UNSUPPORTED HOST CPU')
   message()
-  message('CPU host architecture ' + cpu + ' support is not currently maintained.')
-  message('The QEMU project intends to remove support for this host CPU in')
-  message('a future release if nobody volunteers to maintain it and to')
-  message('provide a build host for our continuous integration setup.')
-  message('configure has succeeded and you can continue to build, but')
-  message('if you care about QEMU on this platform you should contact')
-  message('us upstream at qemu-devel@nongnu.org.')
+  message('Support for CPU host architecture ' + cpu + ' is not currently')
+  message('maintained. The QEMU project does not guarantee that QEMU will')
+  message('compile or work on this host CPU. You can help by volunteering')
+  message('to maintain it and providing a build host for our continuous')
+  message('integration setup.')
+  if get_option('tcg').allowed() and target_dirs.length() > 0
+    message()
+    message('configure has succeeded and you can continue to build, but')
+    message('QEMU will use a slow interpreter to emulate the target CPU.')
+  endif
 endif
 
 if not supported_oses.contains(targetos)
   message()
-  warning('WARNING: SUPPORT FOR THIS HOST OS WILL GO AWAY IN FUTURE RELEASES!')
+  warning('UNSUPPORTED HOST OS')
   message()
-  message('Host OS ' + targetos + 'support is not currently maintained.')
-  message('The QEMU project intends to remove support for this host OS in')
-  message('a future release if nobody volunteers to maintain it and to')
-  message('provide a build host for our continuous integration setup.')
+  message('Support for host OS ' + targetos + 'is not currently maintained.')
   message('configure has succeeded and you can continue to build, but')
-  message('if you care about QEMU on this platform you should contact')
-  message('us upstream at qemu-devel@nongnu.org.')
+  message('the QEMU project does not guarantee that QEMU will compile or')
+  message('work on this operating system. You can help by volunteering')
+  message('to maintain it and providing a build host for our continuous')
+  message('integration setup. This will ensure that future versions of QEMU')
+  message('will keep working on ' + targetos + '.')
+endif
+
+if host_arch == 'unknown' or not supported_oses.contains(targetos)
+  message()
+  message('If you want to help supporting QEMU on this platform, please')
+  message('contact the developers at qemu-devel@nongnu.org.')
 endif