Add appveyor.yml

This file defines the AppVeyor CI (appveyor.com) settings.

It builds using make+bash under MSYS2 so that the current build system
can be used with minimal changes.  It currently only builds configurator
and generates config.h.

The build and test commands for more thorough testing are left as
comments in appveyor.yml so interested parties can use them as a
starting point for future work.

Note that several compiler errors not related to configurator are
printed due to make attempting to generate and include test-depends.
Although Windows-specific code could be added to Makefile to avoid
these, it seemed unwarranted if the compile errors may be fixed soon.

Changes since v2:
- Add reference to AppVeyor results for canonical repo and basic
  instructions to setup AppVeyor for forks.
Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

appveyor.yml

+# AppVeyor CI Configuration
+#
+# Current build status can be viewed at
+# https://ci.appveyor.com/project/dgibson/ccan
+#
+# To build test a fork of this repository using AppVeyor:
+# 1. Visit appveyor.com and create a free account.
+# 2. On the Projects tab, select "New Project" then the project hosting site.
+# 3. Grant OAuth permissions to your project git host.
+# 4. Select the repository for your project fork.
+# 5. Review build results and push updates until the desired result is reached.
+
+version: 0.0.{build}
+
+platform:
+- x86
+- amd64
+
+build_script:
+# Reset %PATH% to avoid msys/cygwin DLL conflicts which cause
+# *** fatal error - cygheap base mismatch detected
+- set PATH=C:\Windows\System32;C:\Windows;C:\Windows\System32\Wbem;C:\msys64\usr\bin
+# Set environment variables for chosen compiler
+- "\"C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\vcvarsall.bat\" %Platform%"
+# Ensure config.h can be generated.
+# Note: Dash options avoid POSIX path conversion by msys
+- "make config.h CC=cl CCAN_CFLAGS=\"-nologo -Zi -FS -W4 -wd4200 -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS\" CFLAGS_FORCE_C_SOURCE=-TC OUTPUT_OPTION=-Fo:$@ DEPGEN= LD=link SHELL=bash"
+# FIXME:  Work in progress.  Disabled due to unfixed compile errors.
+# FIXME:  -j%NUMBER_OF_PROCESSORS% won't work without DEPGEN for config.h
+#         It may be possible to generate .d from cl using /showIncludes
+#         See https://stackoverflow.com/q/37685069
+#- "make tools CC=cl CCAN_CFLAGS=\"-nologo -Zi -FS -W4 -wd4200 -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS\" CFLAGS_FORCE_C_SOURCE=-TC OUTPUT_OPTION=-Fo:$@ DEPGEN= LD=link SHELL=bash"
+#- "make -k CC=cl CCAN_CFLAGS=\"-nologo -Zi -FS -W4 -wd4200 -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS\" CFLAGS_FORCE_C_SOURCE=-TC OUTPUT_OPTION=-Fo:$@ DEPGEN= LD=link SHELL=bash"
+
+test_script:
+# FIXME:  Work in progress.  Disabled due to unfixed compile errors.
+#- "make -k check CC=cl CCAN_CFLAGS=\"-nologo -Zi -FS -W4 -wd4200 -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS\" CFLAGS_FORCE_C_SOURCE=-TC OUTPUT_OPTION=-Fo:$@ DEPGEN= LD=link SHELL=bash"