Build on Windows with WinHTTP

Insert the right libraries to link to to get WinHTTP working. These are
normally done by the build system, but we're building statically so we put
them in ourselves.

We don't write out any dependencies to pkg-config, so let's get rid of it.
To boot, it's not always installed on this platform.

Author: carlosmn

ext/rugged/extconf.rb

@@ -15,6 +15,10 @@ def sys(cmd)
   ret
 end
 
+def on_windows
+  RbConfig::CONFIG['host_os'] =~ /mswin|mingw/
+end
+
 if !(MAKE = find_executable('gmake') || find_executable('make'))
   abort "ERROR: GNU make is required to build Rugged."
 end
@@ -55,7 +59,7 @@ def sys(cmd)
     abort "ERROR: CMake is required to build Rugged."
   end
 
-  if !find_executable('pkg-config')
+  if !on_windows && !find_executable('pkg-config')
     abort "ERROR: pkg-config is required to build Rugged."
   end
 
@@ -66,8 +70,16 @@ def sys(cmd)
       sys("cmake .. -DBUILD_CLAR=OFF -DTHREADSAFE=ON -DBUILD_SHARED_LIBS=OFF -DCMAKE_C_FLAGS=-fPIC -DCMAKE_BUILD_TYPE=RelWithDebInfo -G \"Unix Makefiles\"")
       sys(MAKE)
 
-      pcfile = File.join(LIBGIT2_DIR, "build", "libgit2.pc")
-      $LDFLAGS << " " + `pkg-config --libs --static #{pcfile}`.strip
+	  # "normal" libraries (and libgit2 builds) get all these when they build but we're doing it
+	  # statically so we put the libraries in by hand. It's important that we put the libraries themselves
+	  # in $LIBS or the final linking stage won't pick them up
+      if on_windows
+	    $LDFLAGS << " " + "-L#{Dir.pwd}/deps/winhttp"
+		$LIBS << " -lwinhttp -lcrypt32 -lrpcrt4 -lole32"
+	  else
+        pcfile = File.join(LIBGIT2_DIR, "build", "libgit2.pc")
+        $LDFLAGS << " " + `pkg-config --libs --static #{pcfile}`.strip
+      end
     end
   end