Build x64 zstd from PIC sources.

.gitea/workflows/release.yml

@@ -168,6 +168,7 @@ jobs:
         run: |
           set -eu
           target=x86_64-unknown-linux-gnu
+          unset ZSTD_SYS_USE_PKG_CONFIG
           cargo +${RUST_TOOLCHAIN} build --release --locked --target "$target" \
             --package bds-ui --package bds-cli --package bds-mcp
           rust_lib_dir=$(rustc +${RUST_TOOLCHAIN} --target "$target" --print target-libdir)

crates/bds-ui/tests/packaging_assets.rs

@@ -150,6 +150,7 @@ fn tagged_releases_are_built_and_packaged_with_rust_tools() {
         "CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER",
         "CC_x86_64_unknown_linux_gnu: x86_64-linux-gnu-gcc -fPIC",
         "CXX_x86_64_unknown_linux_gnu: x86_64-linux-gnu-g++ -fPIC",
+        "unset ZSTD_SYS_USE_PKG_CONFIG",
     ] {
         assert!(
             workflow.contains(required),