[SCons] Enable clib_experimental flag

Also, add README.md for clib_experimental interface

SConstruct

@@ -134,6 +134,10 @@ if "clean" in COMMAND_LINE_TARGETS:
         remove_file(name)
     for name in Path("site_scons").glob("**/*.pyc"):
         remove_file(name)
+    for name in Path("include/cantera/clib_experimental").glob("*.h"):
+        remove_file(name)
+    for name in Path("src/clib_experimental").glob("*.cpp"):
+        remove_file(name)
 
     logger.status("Done removing output files.", print_level=False)
 
@@ -364,6 +368,13 @@ config_options = [
         "sphinx_docs",
         "Build HTML documentation for Cantera using Sphinx.",
         False),
+    BoolOption(
+        "clib_experimental",
+        """Build experimental CLib. Requires running 'scons doxygen' and CLib code
+           generation via 'python3 interfaces/sourcegen/run.py --api=clib --output=.'
+           prior to 'scons build' command.
+           """,
+        False),
     BoolOption(
         "run_examples",
         """Run examples to generate plots and outputs for Sphinx Gallery. Disable to

include/cantera/clib_experimental/.gitignore

@@ -0,0 +1 @@
+*.h

include/cantera/clib_experimental/README.md

@@ -0,0 +1,25 @@
+# Cantera – Experimental CLib Interface
+
+This directory and the associated `src/clib_experimental` folder contain an
+experimental re-implementation of Cantera's traditional CLib interface.
+
+## Code Generation
+
+Run the following command from the Cantera root folder:
+
+```
+scons doxygen
+python3 interfaces/sourcegen/run.py --api=clib --output=.
+scons build clib_experimental=y
+```
+
+A rudimentary test suite ensures that code performs as expected:
+
+```
+scons test-clib-experimental
+```
+
+## Status
+
+The experimental CLib Interface is in preview and still missing many features
+needed for parity with the traditional CLib interface.

src/SConscript

@@ -39,6 +39,8 @@ libs = [('base', ['cpp'], baseSetup),
         ('zeroD', ['cpp'], defaultSetup),
         ('clib', ['cpp'], defaultSetup),
         ]
+if env['clib_experimental']:
+    libs.append(('clib_experimental', ['cpp'], defaultSetup))
 
 localenv = env.Clone()
 localenv.Prepend(CPPPATH=[Dir('#include'), Dir('.')])

src/clib_experimental/.gitignore

@@ -0,0 +1 @@
+*.cpp