react-native link on Windows uses incorrect path separator for xcode

[qwertzguy]

Environment

info
React Native Environment Info:
System:
OS: Windows 10
CPU: (4) x64 Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz
Memory: 5.49 GB / 15.89 GB
Binaries:
Yarn: 1.17.3 - C:\Users\gaspa\AppData\Roaming\npm\yarn.CMD
npm: 6.4.1 - C:\Program Files\nodejs\npm.CMD
IDEs:
Android Studio: Version 3.3.0.0 AI-182.5107.16.33.5314842

Description

Running react-native link on windows will use backslashes in the xcode project file project.pbxcode in the HEADER_SEARCH_PATHS.

Resulting in strings like these:
"$(SRCROOT)..\node_modules\neact-native-fs/**",

These will not be parsed correctly by xcode.

The issue is in /packages/platform-ios/src/link/getHeaderSearchPath.js. It should not use the platform path.sep, instead it should always uses forward slashes, regardless of the current platform since xcode only runs on MacOS.

Reproducible Demo

create new project
add library that needs linking, such as react-native-fs
run react-native link react-native-fs on a windows machine
observe result in project.pbxcode file under HEADER_SEARCH_PATHS.

[thymikee]

Would you like to send a PR with a fix? :)

[Taym95]

I would like to submit PR for this issue.