ci: force GNU ld on Linux to fix -ljvm linker error

Recent Rust stable defaults to rust-lld as the linker on
x86_64-unknown-linux-gnu. rust-lld cannot resolve -ljvm against the
Zulu JDK layout installed by actions/setup-java, producing:

    rust-lld: error: unable to find library -ljvm

GNU ld resolves it fine. Add -Clink-arg=-fuse-ld=bfd via workflow-level
RUSTFLAGS so every cargo invocation in Linux CI picks GNU ld, and
extend the per-step RUSTFLAGS values that already set -Ctarget-cpu to
include the same flag (step-level env overrides workflow-level).

Author: andygrove

.github/workflows/iceberg_spark_test.yml

@@ -55,6 +55,10 @@ on:
 env:
   RUST_VERSION: stable
   RUST_BACKTRACE: 1
+  # Force GNU ld on Linux: recent Rust stable defaults to rust-lld on
+  # x86_64-unknown-linux-gnu, and rust-lld cannot resolve -ljvm against the
+  # Zulu JDK layout installed by setup-java. Keep bfd for all cargo invocations.
+  RUSTFLAGS: "-Clink-arg=-fuse-ld=bfd"
 
 jobs:
   # Build native library once and share with all test jobs
@@ -88,7 +92,7 @@ jobs:
         run: |
           cd native && cargo build --profile ci
         env:
-          RUSTFLAGS: "-Ctarget-cpu=x86-64-v3"
+          RUSTFLAGS: "-Ctarget-cpu=x86-64-v3 -Clink-arg=-fuse-ld=bfd"
 
       - name: Save Cargo cache
         uses: actions/cache/save@v5

.github/workflows/pr_build_linux.yml

@@ -49,6 +49,10 @@ on:
 env:
   RUST_VERSION: stable
   RUST_BACKTRACE: 1
+  # Force GNU ld on Linux: recent Rust stable defaults to rust-lld on
+  # x86_64-unknown-linux-gnu, and rust-lld cannot resolve -ljvm against the
+  # Zulu JDK layout installed by setup-java. Keep bfd for all cargo invocations.
+  RUSTFLAGS: "-Clink-arg=-fuse-ld=bfd"
 
 jobs:
 
@@ -166,7 +170,7 @@ jobs:
           # (no LTO, parallel codegen)
           cargo build --profile ci
         env:
-          RUSTFLAGS: "-Ctarget-cpu=x86-64-v3"
+          RUSTFLAGS: "-Ctarget-cpu=x86-64-v3 -Clink-arg=-fuse-ld=bfd"
 
       - name: Upload native library
         uses: actions/upload-artifact@v7

.github/workflows/spark_sql_test.yml

@@ -61,6 +61,10 @@ on:
 env:
   RUST_VERSION: stable
   RUST_BACKTRACE: 1
+  # Force GNU ld on Linux: recent Rust stable defaults to rust-lld on
+  # x86_64-unknown-linux-gnu, and rust-lld cannot resolve -ljvm against the
+  # Zulu JDK layout installed by setup-java. Keep bfd for all cargo invocations.
+  RUSTFLAGS: "-Clink-arg=-fuse-ld=bfd"
 
 jobs:
 
@@ -95,7 +99,7 @@ jobs:
           cd native
           cargo build --profile ci
         env:
-          RUSTFLAGS: "-Ctarget-cpu=x86-64-v3"
+          RUSTFLAGS: "-Ctarget-cpu=x86-64-v3 -Clink-arg=-fuse-ld=bfd"
 
       - name: Upload native library
         uses: actions/upload-artifact@v7