capnproto: fix minimum cmake version for tests

recipes/capnproto/all/test_package/conanfile.py

@@ -9,6 +9,11 @@ class TestPackageConan(ConanFile):
     def build_requirements(self):
         if tools.cross_building(self.settings):
             self.build_requires(str(self.requires["capnproto"]))
+        if self.settings.os == "Macos" and self.settings.arch == "armv8":
+            # Attempting to use @rpath without CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG being
+            # set. This could be because you are using a Mac OS X version less than 10.5
+            # or because CMake's platform configuration is corrupt.
+            self.build_requires("cmake/3.20.1")
 
     def build(self):
         cmake = CMake(self)