[OE-core][PATCH 1/3] cargo.bbclass: Allow using --offline instead of --frozen

["Zoltán Böszörményi" <zboszor@gmail.com>]

Some rust packages complain about the --frozen flag:

| error: the lock file .../Cargo.lock needs to be updated but --frozen was passed to prevent this
| If you want to try to generate the lock file without accessing the network, remove the --frozen flag and use --offline instead.

Add a CARGO_USE_OFFLINE_FLAG = 0/1 flag to allow using --offline
instead of --frozen for such cases.

Use 0 by default to keep using --frozen as the default flag.

Signed-off-by: Zoltán Böszörményi <zboszor@gmail.com>
---
 meta/classes-recipe/cargo.bbclass | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/meta/classes-recipe/cargo.bbclass b/meta/classes-recipe/cargo.bbclass
index b583f84bdf..fe5ce9b023 100644
--- a/meta/classes-recipe/cargo.bbclass
+++ b/meta/classes-recipe/cargo.bbclass
@@ -37,7 +37,10 @@ BUILD_MODE = "${@['--release', ''][d.getVar('DEBUG_BUILD') == '1']}"
 # and will require an up to date Cargo.lock file.
 # This force the package being built to already ship a Cargo.lock, in the end
 # this is what we want, at least, for reproducibility of the build.
-CARGO_BUILD_FLAGS = "-v --frozen --target ${RUST_HOST_SYS} ${BUILD_MODE} --manifest-path=${CARGO_MANIFEST_PATH}"
+# Sometimes --freeze fails because Cargo.lock needs to be modified
+# without version changes. --offline can be used instead.
+CARGO_USE_OFFLINE_FLAG ??= "0"
+CARGO_BUILD_FLAGS = "-v ${@ '--frozen' if d.getVar('CARGO_USE_OFFLINE_FLAG') == '0' else '--offline'} --target ${RUST_HOST_SYS} ${BUILD_MODE} --manifest-path=${CARGO_MANIFEST_PATH}"
 
 # This is based on the content of CARGO_BUILD_FLAGS and generally will need to
 # change if CARGO_BUILD_FLAGS changes.
-- 
2.48.1