[lld][cmake] install symlinks when built standalone

[ZhongRuoyu]

lld installs symlinks with llvm_install_symlink, which relies on the variable LLVM_USE_SYMLINKS to determine whether to use symlinks or copies. Since that variable is defined in llvm's CMakeLists.txt, it may not be defined when lld is built standalone. In that case, default to using symlinks on Unix platforms. Users can still override this by setting LLVM_USE_SYMLINKS manually.

Fixes #151557.

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[llvmbot]

@llvm/pr-subscribers-lld

Author: Ruoyu Zhong (ZhongRuoyu)

Changes

lld installs symlinks with llvm_install_symlink, which relies on the variable LLVM_USE_SYMLINKS to determine whether to use symlinks or copies. Since that variable is defined in llvm's CMakeLists.txt, it may not be defined when lld is built standalone. In that case, default to using symlinks on Unix platforms. Users can still override this by setting LLVM_USE_SYMLINKS manually.

Fixes #151557.

---

Full diff: https://github.com/llvm/llvm-project/pull/160471.diff

1 Files Affected:

• (modified) lld/cmake/modules/AddLLD.cmake (+5)

diff --git a/lld/cmake/modules/AddLLD.cmake b/lld/cmake/modules/AddLLD.cmake
index 37f73afa915f4..21008b5645d00 100644
--- a/lld/cmake/modules/AddLLD.cmake
+++ b/lld/cmake/modules/AddLLD.cmake
@@ -73,6 +73,11 @@ macro(add_lld_tool name)
 endmacro()
 
 macro(add_lld_symlink name dest)
+  # In standalone builds, LLVM_USE_SYMLINKS may not be defined.
+  # In that case, default to using symlinks on Unix platforms.
+  if(NOT DEFINED LLVM_USE_SYMLINKS)
+    set(LLVM_USE_SYMLINKS ${CMAKE_HOST_UNIX})
+  endif()
   get_property(LLVM_DRIVER_TOOLS GLOBAL PROPERTY LLVM_DRIVER_TOOLS)
   if(LLVM_TOOL_LLVM_DRIVER_BUILD
      AND ${dest} IN_LIST LLVM_DRIVER_TOOLS