ninja/mac: Insert a few synthesized Info.plist entries.

Namely, insert BuildMachineOSBuild, DTSDKName, DTSDKBuild, DTXcode, DTXcodeBuild

The values for the synthesized keys are collected at gyp time. The logic for
this is in XcodeEmulation, which makes it add support for this to the make
generator too if someone feels motivated.

The `mac_tool copy-info-plist` command grows support for an arbitrary number
of [key value] arguments, and these values blindly overwrite potential
existing entries from the plist file (this matches Xcode).

BUG=280718
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/23781011

git-svn-id: http://gyp.googlecode.com/svn/trunk@1734 78cadc50-ecff-11dd-a971-7dbc132099af
Actually attach the pool to the link rules on windows.

R=thakis@chromium.org

Review URL: https://codereview.chromium.org/23819070

git-svn-id: http://gyp.googlecode.com/svn/trunk@1735 78cadc50-ecff-11dd-a971-7dbc132099af