[linux] Add missing include in nbio_linux.c.

[ericonr]

Description

On musl-libc, the compiler would print a warning for nbio_linux.c:
"warning: 'struct timespec' declared inside parameter list will not be
visible outside of this definition or declaration", indicating a missing
header defining this structure.

Reviewer

@twinaphex

[inactive123]

hi, this looks like a good enough fix

However, the PR as it currently stands introduces some Travis build failures for the other platforms (I assume the glibc-based Linux compiles).

Can you attempt to fix these while also ensuring musl compatibility at the same time?

https://travis-ci.org/github/libretro/RetroArch/builds/716424461

[ericonr]

Yeah, I saw :/

I'm currently trying to investigate a more correct way of solving this.

[ericonr]

This is probably the more correct header. Is its position in the includes fine?

[ericonr]

For travis, the only issue seems to have been in xcode11 ?

0.03s$ security import dev.p12 -k build.keychain -P $OSX_CERT_PASS -T /usr/bin/codesign
security: SecKeychainItemImport: One or more parameters passed to a function were not valid.
The command "security import dev.p12 -k build.keychain -P $OSX_CERT_PASS -T /usr/bin/codesign" exited with 1.

[inactive123]

The Xcode 11 build failing is just Apple notarization shenanigans, sometimes it works and sometimes it doesn't based on Apples' automated response times. So yeah that is a red herring. Guess we'll merge this and hope for the best with this PR. If it results on build failures on other platforms, I'll get back to you.