Reland "[gn] port 088aa81 (LLVM_HAS_LOGF128)""

This reverts commit 9ebf2f8.
088aa81 relanded in 3613b26.

Author: nico

llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn

@@ -318,6 +318,7 @@ write_cmake_config("llvm-config") {
     "LLVM_ENABLE_ZSTD=",
     "LLVM_FORCE_USE_OLD_TOOLCHAIN=",
     "LLVM_HAS_ATOMICS=1",
+    "LLVM_HAS_LOGF128=",
     "LLVM_HAVE_TFLITE=",
     "LLVM_HOST_TRIPLE=$llvm_current_triple",
     "LLVM_NATIVE_ARCH=$native_target",

llvm/utils/gn/secondary/llvm/test/BUILD.gn

@@ -64,6 +64,7 @@ write_lit_config("lit_site_cfg") {
     "LLVM_ENABLE_HTTPLIB=0",
     "LLVM_ENABLE_ZSTD=0",
     "LLVM_FORCE_VC_REVISION=",
+    "LLVM_HAS_LOGF128=0",
     "LLVM_HAVE_OPT_VIEWER_MODULES=0",
     "LLVM_HOST_TRIPLE=$llvm_current_triple",
     "LLVM_INCLUDE_DXIL_TESTS=0",