Add script to check for Windows, use it to skip sphinx test

The Sphinx scripts need to be updated in much of the same ways that
btest was updated in order to run internal subprocesses and whatnot.

btest

@@ -2227,6 +2227,10 @@ def create_output_handler(options):
             print("cannot open %s: %s" % (options.diagfile, e), file=sys.stderr)
 
     if options.sphinx:
+        if sys.platform == 'win32':
+            print("Sphinx support is disabled on Windows", file=sys.stderr)
+            sys.exit(1)
+
         output_handlers += [SphinxOutput(options)]
 
     if options.xmlfile:

testing/Scripts/is-not-windows

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+case "$OSTYPE" in
+    msys*)
+        exit 1
+        ;;
+    cygwin*)
+        exit 1
+        ;;
+    *)
+        exit 0
+        ;;
+esac

testing/tests/sphinx/run-sphinx

@@ -1,4 +1,5 @@
 # %TEST-REQUIRES: which sphinx-build
+# %TEST-REQUIRES: ${SCRIPTS}/is-not-windows
 #
 # %TEST-EXEC: cp -r %DIR/../../../examples/sphinx/* .
 # %TEST-EXEC: make clean && make text