[gn] port 7f3dcf4 (llvm-ctxprof-util no driver)

Author: nico

llvm/utils/gn/secondary/llvm/tools/llvm-ctxprof-util/BUILD.gn

@@ -1,6 +1,4 @@
-import("//llvm/utils/gn/build/driver_executable.gni")
-
-driver_executable("llvm-ctxprof-util") {
+executable("llvm-ctxprof-util") {
   deps = [
     "//llvm/lib/IR",
     "//llvm/lib/Object",