[PATCH] D125827: [cmake] Don't try creating an executable when detecting the linker

[Louis Dionne via Phabricator via llvm-commits]

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On most platforms, the linker detection command that we run ends up being
something like `clang++ -Wl,-v` or `clang++ -Wl,--version`. This usually
fails with a missing reference to `_main` because we don't have any input
file. However, when compiling for a target that is implicitly freestanding,
the invocation actually succeeds and a dummy `a.out` file is created in
the current working directory. This is extremely annoying because it
creates a `a.out` file at the root of the monorepo when running CMake
configuration from the root.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125827

Files:
  llvm/cmake/modules/AddLLVM.cmake


Index: llvm/cmake/modules/AddLLVM.cmake
===================================================================
--- llvm/cmake/modules/AddLLVM.cmake
+++ llvm/cmake/modules/AddLLVM.cmake
@@ -178,10 +178,10 @@
   endif()
 
   if(LLVM_USE_LINKER)
-    set(command ${CMAKE_C_COMPILER} -fuse-ld=${LLVM_USE_LINKER} ${version_flag})
+    set(command ${CMAKE_C_COMPILER} -fuse-ld=${LLVM_USE_LINKER} ${version_flag} -o /dev/null)
   else()
     separate_arguments(flags UNIX_COMMAND "${CMAKE_EXE_LINKER_FLAGS}")
-    set(command ${CMAKE_C_COMPILER} ${flags} ${version_flag})
+    set(command ${CMAKE_C_COMPILER} ${flags} ${version_flag} -o /dev/null)
   endif()
   execute_process(
     COMMAND ${command}


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