Enable building features in crates on iOS

[buggmagnet]

This PR will enable us building rust crate features by passing a second argument to the build-rust-library.sh script.

For example
build-rust-library.sh mullvad-api api-override

If we need to build more than one feature flag, we can pass in a single argument, all the features separated by spaces
build-rust-library.sh mullvad-api "featureA featureB featureC"

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This change is 

[linear]

IOS-551 Improve the rust library build script to pass feature flags

[niklasberglund]

Reviewable status: 0 of 1 files reviewed, 2 unresolved discussions (waiting on @buggmagnet)

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ios/build-rust-library.sh line 5 at r1 (raw file):

set -euvx

if [ "$#" -gt 2 ]

Nit: the previous condition also guarded against 0 arguments. This condition could for example be [ "$#" -gt 2 ] || [ "$#" -eq 0 ] to also guard against 0 arguments

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ios/build-rust-library.sh line 8 at r1 (raw file):

If we need to build more than one feature flag, we can pass in a single argument, all the features separated by spaces
build-rust-library.sh mullvad-api "featureA featureB featureC"

Found this usage information very helpful, should it be added here as well? Without this info and by looking at the help text here I would assume the syntax build-rust-library.sh mullvad-api featureA featureB featureC is valid but it isn't.

[buggmagnet]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @niklasberglund)

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ios/build-rust-library.sh line 8 at r1 (raw file):

Previously, niklasberglund (Niklas Berglund) wrote…

If we need to build more than one feature flag, we can pass in a single argument, all the features separated by spaces
build-rust-library.sh mullvad-api "featureA featureB featureC"

Found this usage information very helpful, should it be added here as well? Without this info and by looking at the help text here I would assume the syntax build-rust-library.sh mullvad-api featureA featureB featureC is valid but it isn't.

Done.

[niklasberglund]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion

[rablador]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @buggmagnet and @niklasberglund)

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ios/build-rust-library.sh line 16 at r3 (raw file):

# Enable cargo features by passing feature names to this script, i.e. build-rust-library.sh mullvad-api api-override
# If more than one feature flag needs to be enabled, pass in a single argument all the features flags separated by spaces

nit: "argument of all"?

[buggmagnet]

Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @niklasberglund and @rablador)

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ios/build-rust-library.sh line 16 at r3 (raw file):

Previously, rablador (Jon Petersson) wrote…

nit: "argument of all"?

I don't think that suggestion is proper english.

"Pass all the feature flags in a single argument"
"Pass in a single argument all the feature flags"