[x-compile] Fix cross-compiling for AArch64 with an LLVM / Clang

Author: jcelerier

build/cmake/lib/CMakeLists.txt

@@ -9,6 +9,7 @@
 
 project(libzstd C ASM)
 
+message(FATAL_ERROR "CMAKE_SYSTEM_PROCESSOR: '${CMAKE_SYSTEM_PROCESSOR}'")
 set(CMAKE_INCLUDE_CURRENT_DIR TRUE)
 option(ZSTD_BUILD_STATIC "BUILD STATIC LIBRARIES" ON)
 option(ZSTD_BUILD_SHARED "BUILD SHARED LIBRARIES" ON)
@@ -42,7 +43,10 @@ if (MSVC)
     file(GLOB DecompressSources ${LIBRARY_DIR}/decompress/*.c)
     add_compile_options(-DZSTD_DISABLE_ASM)
 else ()
-    file(GLOB DecompressSources ${LIBRARY_DIR}/decompress/*.c ${LIBRARY_DIR}/decompress/*.S)
+    file(GLOB DecompressSources ${LIBRARY_DIR}/decompress/*.c)
+    if(CMAKE_SYSTEM_PROCESSOR MATCHES AMD64)
+       set(DecompressSources ${DecompressSources} ${LIBRARY_DIR}/decompress/huf_decompress_amd64.S)
+    endif()
 endif ()
 file(GLOB DictBuilderSources ${LIBRARY_DIR}/dictBuilder/*.c)
 file(GLOB DeprecatedSources ${LIBRARY_DIR}/deprecated/*.c)