cppstd support added

build.py

@@ -9,4 +9,6 @@ if __name__ == "__main__":
                                  build_policy = "outdated",
                                  upload_dependencies="all")
     builder.add_common_builds(pure_c=False)
+    for settings, options, env_vars, build_requires, reference in builder.items:
+        settings["cppstd"] = "20"
     builder.run()

conanfile.py

@@ -43,7 +43,7 @@ class UnitsConan(ConanFile):
     url = "https://github.com/mpusz/units"
     description = "Physical Units library for C++"
     exports = ["LICENSE.md"]
-    settings = "os", "compiler", "build_type", "arch"
+    settings = "cppstd", "os", "compiler", "build_type", "arch"
     requires = (
         "cmcstl2/2019.03.18@mpusz/stable",
         "gsl-lite/0.33.0@nonstd-lite/stable"
@@ -55,6 +55,10 @@ class UnitsConan(ConanFile):
     }
     generators = "cmake"
 
+    def configure(self):
+        if self.settings.cppstd not in ["20", "gnu20"]:
+            raise ConanInvalidConfiguration("Library units requires at least C++20 support")
+
     def _configure_cmake(self):
         cmake = CMake(self)
         if tools.get_env("CONAN_RUN_TESTS", False):