Merge pull request #14306 from davezarzycki/speculative_apple_lld_fix

[build system] Speculative Apple lld fix

Author: davezarzycki

cmake/modules/AddSwift.cmake

@@ -405,7 +405,8 @@ function(_add_variant_link_flags)
 
   if(NOT SWIFT_COMPILER_IS_MSVC_LIKE)
     find_program(LDLLD_PATH "ld.lld")
-    if((SWIFT_ENABLE_LLD_LINKER AND LDLLD_PATH) OR
+    # Strangely, macOS finds lld and then can't find it when using -fuse-ld=
+    if((SWIFT_ENABLE_LLD_LINKER AND LDLLD_PATH AND NOT APPLE) OR
        ("${LFLAGS_SDK}" STREQUAL "WINDOWS" AND
         NOT "${CMAKE_SYSTEM_NAME}" STREQUAL "WINDOWS"))
       list(APPEND result "-fuse-ld=lld")

cmake/modules/AddSwiftUnittests.cmake

@@ -48,7 +48,8 @@ function(add_swift_unittest test_dirname)
   endif()
 
   find_program(LDLLD_PATH "ld.lld")
-  if(SWIFT_ENABLE_LLD_LINKER AND LDLLD_PATH)
+  # Strangely, macOS finds lld and then can't find it when using -fuse-ld=
+  if(SWIFT_ENABLE_LLD_LINKER AND LDLLD_PATH AND NOT APPLE)
     set_property(TARGET "${test_dirname}" APPEND_STRING PROPERTY
       LINK_FLAGS " -fuse-ld=lld")
   elseif(SWIFT_ENABLE_GOLD_LINKER AND