build.plat,setup: fix Jinja2 dependency.

Jinja2 version 2.11 has a broken dependency constraint that allows its
dependency on markupsafe to pull in a version that it is not actually
compatible with the interface of. Fix this by upgrading the dependency
to `~=3.0`. This requires a small patch to the code to replace the
deprecated `@jinja2.contextfunction` decorator with the replacement
`@jinja2.pass_context`since `@jinja2.contextfunction` is removed in
Jinja2 version 3.1.0.

amaranth/build/plat.py

@@ -375,7 +375,7 @@ class TemplatedPlatform(Platform):
             else:
                 return jinja2.Undefined(name=var)
 
-        @jinja2.contextfunction
+        @jinja2.pass_context
         def invoke_tool(context, name):
             env_var = tool_env_var(name)
             if context.parent["syntax"] == "sh":

setup.py

@@ -43,7 +43,7 @@ setup(
         "importlib_metadata; python_version<'3.8'",  # for __version__ and amaranth._toolchain.yosys
         "importlib_resources; python_version<'3.9'", # for amaranth._toolchain.yosys
         "pyvcd~=0.2.2", # for amaranth.pysim
-        "Jinja2>=2.11,<4.0", # for amaranth.build
+        "Jinja2~=3.0",  # for amaranth.build
     ],
     extras_require={
         # this version requirement needs to be synchronized with the one in amaranth.back.verilog!