test(rust): try earthly no-cache and fix doc artifact

Signed-off-by: bkioshn <bkioshn@gmail.com>

rust/Earthfile

@@ -21,7 +21,6 @@ COPY_SRC:
 # builder : Set up our target toolchains, and copy our files.
 builder:
     DO rust-ci+SETUP
-    RUN --no-cache
 
 # sync-cfg: Synchronize local config with CI version.
 # Must be run by the developer manually.
@@ -53,6 +52,7 @@ check:
 build:
     FROM +builder-src
 
+    RUN --no-cache
     DO rust-ci+EXECUTE \
         --cmd="/scripts/std_build.py" \
         --args1="--libs=c509-certificate --libs=cardano-blockchain-types --libs=cardano-chain-follower --libs=hermes-ipfs" \
@@ -65,7 +65,7 @@ build:
         --coverage="cat-libs.coverage.info" \
         --docs="true"
 
-    SAVE ARTIFACT target/$TARGETARCH/doc doc
+    SAVE ARTIFACT target/doc doc
     SAVE ARTIFACT target/release/cbork cbork
 
 # build-src-check: Check for any caching issues with the source we are building against.