test: Don't distinguish between wasi, wasip1 to use OS=wasi condition

We already have several uses of `OS=wasi` in the test suites, and the
condition should match all the wasi targets regardless of the version.

test/lit.cfg

@@ -400,6 +400,11 @@ if run_vers.endswith('-simulator'):
 else:
     run_environment=''
 
+# Don't distinguish between wasi, wasip1, and so on to use OS=wasi condition in
+# the test suites.
+if run_os.startswith('wasi'):
+    run_os = 'wasi'
+
 # Parse the host triple
 (host_cpu, host_vendor, host_os, host_vers) = re.match('([^-]+)-([^-]+)-([^0-9-]+)(.*)', config.host_triple).groups()