Enable usage of rust mirrors

Hello,

this is actually a duplication of this ticket. There has never been a response to this ticket, so I assume the request was perhaps not precise enough. I will try to be more precise.

There can be reasons that there is a need for using a mirror of static.rust-lang.org. Inside meta-rust-bin, there is the variable RUST_BASE_URI which is defined in classes/rust_bin-common.bbclass. This variable is set with the := assignment which does no allow the variable to be pre-defined, e.g. at local.conf. bbappending is also not possible for bbclasses. By simply changing the assignment into ?= would do the trick. E.g.:

-RUST_BASE_URI := "https://static.rust-lang.org"
+RUST_BASE_URI ?= "https://static.rust-lang.org"

A 2nd change that is required to use RUST_BASE_URI everywhere. Currently, this variable is not used inside the recipes-devtools/rust/cargo-bin-cross_.bb recipes. Instead, the string "https://static.rust-lang.org" is used. E.g.

 def cargo_url(triple):
     URLS = {
-        "aarch64-unknown-linux-gnu": "https://static.rust-lang.org/dist/2024-06-13/cargo-1.79.0-aarch64-unknown-linux-gnu.tar.gz",
-        "arm-unknown-linux-gnueabi": "https://static.rust-lang.org/dist/2024-06-13/cargo-1.79.0-arm-unknown-linux-gnueabi.tar.gz",
-        "arm-unknown-linux-gnueabihf": "https://static.rust-lang.org/dist/2024-06-13/cargo-1.79.0-arm-unknown-linux-gnueabihf.tar.gz",
-        "armv7-unknown-linux-gnueabihf": "https://static.rust-lang.org/dist/2024-06-13/cargo-1.79.0-armv7-unknown-linux-gnueabihf.tar.gz",
-        "i686-unknown-linux-gnu": "https://static.rust-lang.org/dist/2024-06-13/cargo-1.79.0-i686-unknown-linux-gnu.tar.gz",
-        "x86_64-unknown-linux-gnu": "https://static.rust-lang.org/dist/2024-06-13/cargo-1.79.0-x86_64-unknown-linux-gnu.tar.gz",
+        "aarch64-unknown-linux-gnu": "${RUST_BASE_URI}/dist/2024-06-13/cargo-1.79.0-aarch64-unknown-linux-gnu.tar.gz",
+        "arm-unknown-linux-gnueabi": "${RUST_BASE_URI}/dist/2024-06-13/cargo-1.79.0-arm-unknown-linux-gnueabi.tar.gz",
+        "arm-unknown-linux-gnueabihf": "${RUST_BASE_URI}/dist/2024-06-13/cargo-1.79.0-arm-unknown-linux-gnueabihf.tar.gz",
+        "armv7-unknown-linux-gnueabihf": "${RUST_BASE_URI}/dist/2024-06-13/cargo-1.79.0-armv7-unknown-linux-gnueabihf.tar.gz",
+        "i686-unknown-linux-gnu": "${RUST_BASE_URI}/dist/2024-06-13/cargo-1.79.0-i686-unknown-linux-gnu.tar.gz",
+        "x86_64-unknown-linux-gnu": "${RUST_BASE_URI}/dist/2024-06-13/cargo-1.79.0-x86_64-unknown-linux-gnu.tar.gz",
     }

My 3rd demand comes into play when looking into the internal structure of the static.rust-lang.org repository. The URI for fetching artifacts is actually https://static.rust-lang.org/dist/. However, the files are found one level above, sorting artifacts by release dates. The delegation happens with the channel.toml files. If these channel.toml configurations are not recognized by a mirror, the files are not found.

For cargo downloading, the URI is actually containing these paths currently, so there things are working as expected. E.g.

$ bitbake -e cargo-bin-cross-x86_64 | grep ^SRC_URI
SRC_URI="https://static.rust-lang.org/dist/2024-06-13/cargo-1.79.0-x86_64-unknown-linux-gnu.tar.gz;md5sum=4a89780dc045b3fe221b4507ed63bfd3;sha256sum=d394298cfd4a51eaf85607cceb33a1d83cbe723365687d7055f4b68e065a72fe;downloadname=cargo-bin-cross-x86_64-1.79.0-x86_64-unknown-linux-gnu.tar.gz"

For rust downloading, the URI is lacking the date directory level, so there downloading fails. E.g.

$ bitbake -e rust-bin-cross-x86_64 | grep ^SRC_URI
SRC_URI="https://static.rust-lang.org/dist/rustc-1.79.0-x86_64-unknown-linux-gnu.tar.gz;md5sum=a0cac6f2de82fbf573c7706a766466e6;sha256sum=36e59d225cc4c35f4d63c276c94a5e5cba5c8083275c3990ae7cae6842f9109f https://static.rust-lang.org/dist/rust-std-1.79.0-x86_64-unknown-linux-gnu.tar.gz;md5sum=489611626b01cf4f882df76e3cfe7306;sha256sum=037906a372ec87f8fd7ab45efa645bcc4fbf981f534e31534c6f16ce628fddb6;subdir=rust-std https://static.rust-lang.org/dist/rust-std-1.79.0-x86_64-unknown-linux-gnu.tar.gz;md5sum=489611626b01cf4f882df76e3cfe7306;sha256sum=037906a372ec87f8fd7ab45efa645bcc4fbf981f534e31534c6f16ce628fddb6;subdir=rust-std"

The demand is to also add the date level to the rust URI to be more robust when not having a "real" rust mirror in place.

Start with classes/rust_bin-common.bbclass and the recipes-devtools/rust/cargo-bin-cross_.bb recipes, then inspect the rust-bin-cross recipe SRC_URI values using the bitbake -e commands shown. Verify that RUST_BASE_URI can be overridden, cargo and rust downloads use it, and rust URLs include the date directory required by mirrors.