Properly discover the target triple. (vgvassilev#677)

This patch helps enabling the osx target's SDKROOT.

test/lit.site.cfg.in

@@ -2,13 +2,14 @@ import sys
 
 ## Autogenerated by LLVM/clad configuration.
 # Do not edit!
+llvm_version_major = @LLVM_VERSION_MAJOR@
 config.llvm_src_root = "@LLVM_SOURCE_DIR@"
 config.llvm_obj_root = "@LLVM_BINARY_DIR@"
 config.llvm_tools_dir = "@LLVM_TOOLS_DIR@"
 config.llvm_libs_dir = "@LLVM_LIBS_DIR@"
 config.llvm_lib_output_intdir = "@LLVM_LIBRARY_OUTPUT_INTDIR@"
 config.clad_obj_root = "@CLAD_BINARY_DIR@"
-config.target_triple = "@TARGET_TRIPLE@"
+config.target_triple = "@LLVM_TARGET_TRIPLE@" if llvm_version_major > 11 else "@TARGET_TRIPLE@"
 config.shlibext = "@TARGET_SHLIBEXT@"
 config.have_enzyme = "@CLAD_ENABLE_ENZYME_BACKEND@"