cjdns @21.1 "-march=native" not supported on Apple M1

[eric-j-ason]

This is the output when trying to install:

% port install cjdns
Warning: The macOS 11.2 SDK does not appear to be installed. Ports may not build correctly.
Warning: You can install it as part of the Xcode Command Line Tools package by running `xcode-select --install'.
--->  Computing dependencies for cjdns
--->  Building cjdns
Error: Failed to build cjdns: command execution failed
Error: See /Users/eand/macports/var/macports/logs/_Users_eand_macports_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_net_cjdns/cjdns/mai\
n.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
Error: Processing of port cjdns failed

My understanding is that the warning about "macOS 11.2 SDK" isn't the issue here. Rather, the actual error, found in the log file, is this:

clang: error: the clang compiler does not support '-march=native'

[kencu (Ken)]

​https://stackoverflow.com/questions/65966969/why-does-march-native-not-work-on-apple-m1

​https://developer.apple.com/forums/thread/672654

I would think it would be better for clang to just eat that flag and ignore it on arm, rather than error, but it would seem upstream felt otherwise...

another layer of complexity now to everything, to never pass that flag if arm is in the build architectures.... sigh.

[ryandesign (Ryan Carsten Schmidt)]

It's not just about arm. We don't want to use -march=native on Intel either (we want to build portable software that works on any Intel CPU) unless the user selects the +native variant. Encountering this problem has alerted us to the fact that we are building wrong on Intel, giving us the opportunity to fix it.

[l2dy (Zero King)]

In 69131659877c2d73936789f5ba5e37ee7db45357/macports-ports (master):

cjdns: fix build on M1

Closes: #62598

[l2dy (Zero King)]

I have removed the -march=native flag. If the build still fails, you should bring it to upstream.