Remove end of line comments from xcconfig build settings

[damirdavletov]

Context 🕵️‍♀️

In our projects we use xcconfig files for project configuration and in some cases we use in-line comments like:
PRODUCT_NAME = $(TARGET_NAME) // FIXME: ideally, should probably be $(TARGET_NAME:rfc1034identifier), but some of our existing names will change

What 🌱

Retrieving the above settings with the code like
let productName = target.buildConfigurationList?.configuration(name: "Release")?.buildSettings["PRODUCT_NAME"]
Will produce result:
"$(TARGET_NAME) // FIXME: ideally, should probably be $(TARGET_NAME:rfc1034identifier), but some of our existing names will change"
Expected result:
"$(TARGET_NAME)"

Proposal 🎉

Improve XCConfigParser.settingRegex to cut off end of line comments