a0daea459cf4812fbdda9a7ead131a73f5856c09 [build] depends macOS: point --sysroot to SDK (Sjors Provoost)
Pull request description:
Fixes errors like `fatal error: 'unistd.h' file not found` when building depends on macOS.
Replaces #14352 (which doesn't work on Catalina).
ACKs for top commit:
jonasschnelli:
utACK a0daea459cf4812fbdda9a7ead131a73f5856c09
Tree-SHA512: 995b1e1e84e635b32d1d4038bc63730c94a7c318b7240f6d62825977e5c97fe52c5aa5a0f39070beb0df8271dd294b36d6b5cf7f09ad07494fb15d5bd4d77f68
* Retry downloading of depends sources 3 times
* Manually invoke apt-get update and install instead of using addon
This allows us to use travis_retry on these operations.
* Add exception for depends/Makefile in .gitignore
* Remove --retry from curl call
This avoids future confusion as we don't rely on curl anymore to properly
retry downloads. curls does only retry on transient errors, while Travis
might cause all kinds of errors which circumvent the retry logic of curl.
