Try to fix more CI failures related to C++20

.cirrus.yml

@@ -22,7 +22,7 @@ linux_task:
     matrix:
         - name: linux_clang
           container:
-              image: silkeh/clang:7
+              image: silkeh/clang:10
           clang_script:
               - apt-get -y install pkg-config libncursesw5-dev
           env:
@@ -36,7 +36,7 @@ linux_task:
 
 macos_task:
     osx_instance:
-        image: mojave-base
+        image: big-sur-base
     matrix:
         - name: macos_clang
           env:

src/units.hh

@@ -5,6 +5,7 @@
 #include "hash.hh"
 
 #include <type_traits>
+#include <compare>
 
 namespace Kakoune
 {

src/utils.hh

@@ -4,6 +4,7 @@
 #include "assert.hh"
 
 #include <memory>
+#include <concepts>
 
 namespace Kakoune
 {