cargo_fetch PG, rust, cargo: Add support for using legacysupport PG

[cjones051073]

https://trac.macports.org/ticket/62656

Support older systems requiring legacy support

- Patch bootstrapping binaries to use legacysupport dylib for missing libSystem calls
- Wrap underlying compiler commands used by rust/cargo to enforce use of legacy support flags

Fixes things perfectly for macOS10.9. rust, cargo install fine and was able to build a number of cargo/rust based ports.

Work on older systems is WIP, as currently failing for other unknown reasons.

@kencu FYI

Description

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS x.y
Xcode x.y

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?

[macportsbot]

Notifying maintainers:
@herbygillot for port cargo, rust.
@g5pw for port rust.

[herbygillot]

I've gotta be honest, I'm still pretty wary of doing any legacysupport modifications to anything Rust-related.

[cjones051073]

I've gotta be honest, I'm still pretty wary of doing any legacysupport modifications to anything Rust-related.

I understand, there was problems last time. I know why there was problems last time this was tried, and this time I avoid them. For one, last time the use of legacysupport was not limited to 10.9 or older, so it was also used on 10.10 and 10.11. This time it is currently limited to 10.9 and older, so will only affect platforms rust currently does not build on anyway.

I am 99.9% sure on 10.10 and newer the changes here have no affect what so ever.

The other reason it shouldn’t be a problem this time is i use the static link option, which avoids the issue with the internal llvm build, and also wrap the commands to make completely sure the right flags are used.

[cjones051073]

Tested now extensively on a number of systems. Fixes build of rust itself on 10.9, and also on 10.{10-11} a number of port builds that currently fail due to missing features in libSystem, like clock_gettime.