'make update-build-docs' fails with 'fixpath Unknown argument: --toc' on Windows

[Jorn Vernee]

Hello,

I'm updating some documentation for the panama repo foreign branch [1].

When running `make update-build-docs` I get the following output:

```
$ make update-build-docs
Building target 'update-build-docs' in configuration 
'windows-x86_64-server-release'
fixpath Unknown argument: --toc
fixpath Unknown argument: --toc
fixpath Unknown argument: --toc
make[3]: *** [UpdateBuildDocs.gmk:50: 
/cygdrive/h/cygwin64/home/Jorn/cygwin-projects-new/panama/doc/building.html] 
Error 127
make[3]: *** Waiting for unfinished jobs....
make[3]: *** [UpdateBuildDocs.gmk:58: 
/cygdrive/h/cygwin64/home/Jorn/cygwin-projects-new/panama/doc/testing.html] 
Error 127
make[3]: *** [UpdateBuildDocs.gmk:66: 
/cygdrive/h/cygwin64/home/Jorn/cygwin-projects-new/panama/doc/panama_foreign.html] 
Error 127
make[2]: *** [make/Main.gmk:417: update-build-docs] Error 2

ERROR: Build failed for target 'update-build-docs' in configuration 
'windows-x86_64-server-release' (exit code 2)

=== Output from failing command(s) repeated here ===
* For target support_markdown_building_building.md:
fixpath Unknown argument: --toc
* For target support_markdown_panama_foreign_panama_foreign.md:
fixpath Unknown argument: --toc
* For target support_markdown_testing_testing.md:
fixpath Unknown argument: --toc

* All command lines available in 
/cygdrive/h/cygwin64/home/Jorn/cygwin-projects-new/panama/build/windows-x86_64-server-release/make-support/failure-logs.
=== End of repeated output ===

No indication of failed target found.
Hint: Try searching the build log for '] Error'.
Hint: See doc/building.html#troubleshooting for assistance.

make[1]: *** [/home/Jorn/cygwin-projects-new/panama/make/Init.gmk:310: 
main] Error 2
make: *** [/home/Jorn/cygwin-projects-new/panama/make/Init.gmk:186: 
update-build-docs] Error 2
```

Is this a know issue? Is this supported on Windows?

Thanks,
Jorn

[1] : http://hg.openjdk.java.net/panama/dev/shortlog/b981c23cb71e