[contrib][linux] Disable ASM in the kernel

Disable ASM in the kernel for now. It requires a few changes & setup to
get working. Instead of doing it in a zstd version update, I'd prefer to
package that change as a single patch, and propose it separately from
the version update. This makes the version update easier, and reduces
some risk.

contrib/linux-kernel/Makefile

@@ -56,7 +56,9 @@ libzstd:
 		-DZSTD_HAVE_WEAK_SYMBOLS=0 \
 		-DZSTD_TRACE=0 \
 		-DZSTD_NO_TRACE \
+		-DZSTD_DISABLE_ASM \
 		-DZSTD_LINUX_KERNEL
+	rm linux/lib/zstd/decompress/huf_decompress_amd64.S
 	mv linux/lib/zstd/zstd.h linux/include/linux/zstd_lib.h
 	mv linux/lib/zstd/zstd_errors.h linux/include/linux/
 	cp linux_zstd.h linux/include/linux/zstd.h
@@ -104,4 +106,5 @@ test: libzstd
 
 .PHONY: clean
 clean:
-	$(RM) -rf linux test/test test/static_test
+	$(RM) -rf linux
+	$(MAKE) -C test clean

contrib/linux-kernel/linux.mk

@@ -29,7 +29,6 @@ zstd_compress-y := \
 
 zstd_decompress-y := \
 		zstd_decompress_module.o \
-		decompress/huf_decompress_amd64.o \
 		decompress/huf_decompress.o \
 		decompress/zstd_ddict.o \
 		decompress/zstd_decompress.o \

contrib/linux-kernel/test/Makefile

@@ -45,4 +45,5 @@ clean:
 	$(RM) -f $(LINUX_ZSTDLIB)/*.o
 	$(RM) -f $(LINUX_ZSTDLIB)/**/*.o
 	$(RM) -f *.o *.a
+	$(RM) -f static_test
 	$(RM) -f test