build(rust): link migrated code into native libraries

Build feature-matched Rust archives for the native Make library path. Flatten
their members into libzstd.a so static consumers resolve C-to-Rust and
Rust-to-C references in one archive, and whole-archive link shared outputs so
every migrated public ABI export remains available.

Rust compression and decompression features now mirror the C partial-library
switches. This prevents compression-only artifacts from retaining DDict
references to decompression-only C helpers.

Add a C archive smoke test that round-trips data and exercises the DDict
lifecycle through lib/libzstd.a, rather than direct test-object links.

Test Plan:
- cargo fmt, strict Clippy, cargo test --all-targets, release build
- Rust checks with compression-only, decompression-only, and no features
- full, partial, forced-HUF, and 32-bit static/shared Make library probes
- test-rust-lib-smoke, fuzzer, zstreamtest, and invalidDictionaries

Refs: rust/README.md

tests/Makefile

@@ -308,6 +308,13 @@ largeDictionary: $(ZSTDMT_OBJECTS) $(PRGDIR)/datagen.c largeDictionary.c
 CLEAN += invalidDictionaries
 invalidDictionaries : $(ZSTD_OBJECTS) invalidDictionaries.c
 
+# Exercise the public static archive as an external C consumer would. This
+# catches a nested Rust archive or unresolved C/Rust cycle that direct object
+# links cannot expose.
+CLEAN += rustLibSmoke
+rustLibSmoke : $(LIB_BINDIR)/libzstd.a rustLibSmoke.c
+	$(LINK.c) $(filter %.c,$^) $(filter %.a,$^) -o $@$(EXT)
+
 CLEAN += legacy
 legacy : CPPFLAGS += -UZSTD_LEGACY_SUPPORT -DZSTD_LEGACY_SUPPORT=4
 legacy : $(ZSTD_FILES) legacy.c
@@ -413,7 +420,7 @@ check: test-zstd
 fuzztest: test-fuzzer test-zstream test-decodecorpus
 
 .PHONY: test
-test: test-zstd test-cli-tests test-fullbench test-fuzzer test-zstream test-invalidDictionaries test-legacy test-decodecorpus
+test: test-zstd test-cli-tests test-fullbench test-fuzzer test-zstream test-invalidDictionaries test-rust-lib-smoke test-legacy test-decodecorpus
 ifeq ($(QEMU_SYS),)
 test: test-pool
 endif
@@ -491,6 +498,10 @@ test-largeDictionary: largeDictionary
 test-invalidDictionaries: invalidDictionaries
 	$(QEMU_SYS) ./invalidDictionaries
 
+.PHONY: test-rust-lib-smoke
+test-rust-lib-smoke: rustLibSmoke
+	$(QEMU_SYS) ./rustLibSmoke
+
 test-legacy: legacy
 	$(QEMU_SYS) ./legacy