[util] Document required VCS version

We don't actually run anything that checks this at the moment, but at
least we now have it written down somewhere.

doc/02_user/system_requirements.rst

@@ -10,7 +10,7 @@ Please `file an issue <https://github.com/lowRISC/ibex/issues>`_ if you experien
 - Synopsys Design Compiler
 - Xilinx Vivado
 - Verilator, version |tool_requirements.verilator| and up.
-- Synopsys VCS
+- Synopsys VCS, version at least |tool_requirements.vcs|.
 - Cadence Incisive/Xcelium
 - Mentor Questa
 - Aldec Riviera Pro

doc/conf.py

@@ -12,12 +12,19 @@
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
 import os
-# import sys
-# sys.path.insert(0, os.path.abspath('.'))
+import sys
 
 # Source top directory
 topsrcdir = os.path.join(os.path.dirname(__file__), '..')
 
+old_sys_path = sys.path
+try:
+    sys.path.append(os.path.join(topsrcdir, 'util'))
+    import check_tool_requirements as ctr
+finally:
+    sys.path = old_sys_path
+
+
 numfig=True
 numfig_format = {'figure': 'Figure %s', 'table': 'Table %s', 'code-block': 'Listing %s'}
 
@@ -164,7 +171,8 @@ texinfo_documents = [
 
 # Add minimum versions of required tools as variables for use inside the
 # documentation.
-exec(open(os.path.join(topsrcdir, 'tool_requirements.py')).read())
+tool_reqs = ctr.read_tool_requirements()
 rst_epilog = ""
-for tool_name, tool_version in __TOOL_REQUIREMENTS__.items():
-    rst_epilog += ".. |tool_requirements.{}| replace:: {}\n".format(tool_name, tool_version)
+for tool, req in tool_reqs.items():
+    rst_epilog += (".. |tool_requirements.{}| replace:: {}\n"
+                   .format(tool, req.min_version))

tool_requirements.py

@@ -6,5 +6,9 @@
 # and inserted into the Sphinx-generated documentation.
 __TOOL_REQUIREMENTS__ = {
     'verilator': '4.028',
-    'edalize':   '0.2.0'
+    'edalize':   '0.2.0',
+    'vcs': {
+        'min_version': '2020.03-SP2',
+        'as_needed': True
+    }
 }