Replace system() with posix_spawn in LaunchFileExplorer.

[apemax]

This commit replaces system() with posix_spawn.

[Triang3l]

Can you please squash the two commits into one as the new one largely supersedes the first commit?

[apemax]

Implemented all corrections apart from the extern char** environ; being global, However it seems like the only way for it to work is by being global. getenv can be used but it would require a lot more code to get all the required environment variables. Any thoughts on this or anything else outstanding?

Will squash these commits once LaunchFileExplorer is finalised.

[Razzile]

@JohnHenry150 This tone is not appreciated on this project, nor are any of the issues you've mentioned relevant to the PR in any way